What are the basic Python questions asked in interview?

What are the basic Python questions asked in interview? : introductory Python interview questions Q1 . What distinguishes Python’s list and tuples? Q2. What are Python’s main characteristics? Q3. Python is a programming language. Python is an interpreted language. Q5. What exactly is PEP 8? How does Python manage memory? Q18 Q19. What in Python is a namespace?
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Data types make programming easier and are more powerful and efficient than most that can be created from scratch. In this article , I’ll walk you through some Python interview questions on data types.

Table of Contents

What are Data Types?

An established set of values and operations on data constitute a data type. A data type’s implementation is an expression of data and operations using a particular programming language, such as Java, C, or Python.

Now before moving to the Python interview questions based on data types let’s have a quick look at the inbuilt data types that we get in the Python programming language:

Data TypesExamples

Numbers 1234, 3.1415, 3+4j
Strings ‘spam’, “Bob’s”, b’a\x01c’,
Lists [1, [2, ‘three’], 4.5]
Dictionaries {‘food’: ‘spam’, ‘taste’: ‘yum’}
Tuples (1, ‘spam’, 4, ‘U’)
Sets set(‘abc’), {‘a’, ‘b’, ‘c’}

Name four of the main data types in Python

Numbers, strings, lists, dictionaries, tuples, files, and sets are generally considered the main types of data. Types, None, and Booleans are sometimes also classified this way. The integer, floating-point, complex, fraction and decimal are numerical data types and simple strings and Unicode strings in Python 2 and text strings and byte strings in Python 3 are the types of string data types.

Why arethese data types known as Python’s core data types?

They are known as the core data types because they are part of the Python language itself and are always available to create other objects, you usually need to call functions in imported modules

Most of the data types have a specific syntax for generating objects: “spam”, for example, is an expression that creates a string and determines the set of operations that can be applied to it. For this reason, main types are built intoPython syntax. Instead, you must call the built-in open function to create a file object.

What does immutable mean and what three types of Python core data types are considered immutable?

An immutable data type is a type of object which cannot be modified after its creation. Numbers, strings, and tuples in Python fall into this category. Although you cannot modify an immutable object in place, you can always create a new one by running an expression.

What does sequence meanand which three types of data fall into this category?

A sequence data type is a collection of objects ordered by a specific position. In Python, Strings, lists, and tuples are the data types based on sequences. The Sequences share common sequence operations, such as indexing, concatenation, and slicing, but also have type-specific method calls.

What does mapping mean and what kind of data type is based on mapping?

The term mapping refers to an object that maps keys toassociated values. The Python dictionary is the only type of mapping in the base typeset. Mappings do not maintain any left-to-right position order; they support access to stored data by key, as well as type-specific method calls.

What is polymorphism and why should you care?

Polymorphism means that the meaning of an operation (like a+) depends on the objects being operated This turns out to be a key idea behind good use of Python, not coercing code to specific types makes thatcode automatically applied to many types

I hope you liked this article on Python interview questions on Data Types Feel free to ask your valuable questions in the comments section below

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What are the basic Python questions asked in interview?

Is Python good for interview? : Python is not a good choice for coding interviews, so there is no point in worrying about it. It’s crucial that you comprehend any programming language’s fundamental concepts clearly. Whether you program in Java, C, C, or another language is irrelevant.
How do I practice Python programming interview? : Use enumerate() to iterate over both indices and values in Python coding interviews. Effectively use f-strings to debug problematic code with breakpoint()Format strings. Using specific arguments, sort lists. To save memory, swap out list comprehensions for generators.
What are the Python questions asked in TCS interview? : Python is an interpreted language. Here are some common Python interview questions for new graduates. What are the key features of Python? How is memory managed in Python? What is PYTHONPATH? What are Python Modules? What is the difference between lists and tuples? What is PEP 8?
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Python was developed by Guido van Rossum and was released first on February 20, 1991. It is one of the most widely-used and loved programming languages and is interpreted in nature thereby providing flexibility of incorporating dynamic semantics. It is also a free and open-source language with very simple and clean syntax. Thismakes it easy for developers to learn python. Python also supports object-oriented programming and is most commonly used to perform general-purpose programming. 

Python’s popularity is exploding because of its simplicity and capacity to perform multiple functionalities with fewer lines of code. Due to its capability to support powerful computations using powerful libraries, Python is also used in a variety of other domains, including machine learning, artificial intelligence, web development, web scraping, and others. Python developers are in great demand in India and all over the world as a result of this. Businesses are eager to provide these developers with incredible perks and benefits.

We haveclassified them into the following sections:

  • Python Interview Questions for Freshers
  • Python Interview Questions for Experienced
  • Python OOPS Interview Questions
  • Python Pandas Interview Questions
  • Numpy Interview Questions
  • Python Libraries Interview Questions
  • Python Programming Examples

Python is a general-purpose, high-level, interpreted programming language. With the appropriate tools and libraries, a general-purpose language like this one can be used to create almost any kind of application. Additionally, Python supports objects, modules, threads, handling of exceptions, and automatic memory management that aid in modeling real-world problems and creating applications to solve them.

Benefits of using Python:

  • Python is a general-purposeprogramming language that has a simple, easy-to-learn syntax that emphasizes readability and therefore reduces the cost of program maintenance. Moreover, the language is capable of scripting, is completely open-source, and supports third-party packages encouraging modularity and code reuse.
  • Its high-level data structures, combined with dynamic typing and dynamic binding, attract a huge community ofdevelopers for Rapid Application Development and deployment.

2. What is a dynamically typed language?

Before we understand a dynamically typed language, we should learn about what typing is. Typing refers to type-checking in programming languages. In astrongly-typed language, such as Python, “1” + 2 will result in a type error since these languages don’t allow for “type-coercion” (implicit conversion of data types). On the other hand, a weakly-typed language, such as Javascript, will simply output “12” as result.

Type-checking can be done at two stages –

  • Static – Data Types are checked before execution.
  • Dynamic -Data Types are checked during execution.

Python is an interpreted language, executes each statement line by line and thus type-checking is done on the fly, during execution. Hence, Python is a Dynamically Typed Language.

3. What is an Interpreted language?

An Interpreted language executes its statements line by line.Languages such as Python, Javascript, R, PHP, and Ruby are prime examples of Interpreted languages. Programs written in an interpreted language runs directly from the source code, with no intermediary compilation step.

4. What is PEP 8 and why is it important?

PEP stands for Python Enhancement Proposal. A PEP is an official design document providing information to the Python community, ordescribing a new feature for Python or its processes. PEP 8 is especially important since it documents the style guidelines for Python Code. Apparently contributing to the Python open-source community requires you to follow these style guidelines sincerely and strictly.

5. What is Scope in Python?

Every object in Python functions within a scope. A scope is a block of code where an object in Python remainsrelevant. Namespaces uniquely identify all the objects inside a program. However, these namespaces also have a scope defined for them where you could use their objects without any prefix. A few examples of scope created during code execution in Python are as follows:

  • A local scope refers to the local objects available in the current function.
  • A global scope refers to the objects available throughout the code execution since their inception.
  • A module-level scope refers to the global objects of the current module accessible in the program.
  • An outermost scope refers to all the built-in names callable in the program. The objects in this scope are searched last to find the name referenced.

Note: Local scope objects can be synced with global scope objects using keywords such as global.

6. Whatare lists and tuples? What is the key difference between the two?

Lists and Tuples are both sequence data types that can store a collection of objects in Python. The objects stored in both sequences can have different data types. Lists are represented with square brackets ['sara', 6, 0.19], while tuples are represented with parantheses ('ansh', 5, 0.97).But what is the real difference betweenthe two? The key difference between the two is that while lists are mutable, tuples on the other hand are immutable objects. This means that lists can be modified, appended or sliced on the go but tuples remain constant and cannot be modified in any manner. You can run the following example on Python IDLE to confirm the difference:

my_tuple = ('sara', 6, 5, 0.97)my_list = ['sara', 6, 5, 0.97]print(my_tuple[])     # output => 'sara'print(my_list[])     # output => 'sara'my_tuple[] = 'ansh'    # modifying tuple => throws an errormy_list[] = 'ansh'    # modifying list => list modifiedprint(my_tuple[])     # output => 'sara'print(my_list[])     # output => 'ansh'

7. What are the common built-in datatypes in Python?

There are several built-in data types in Python. Although, Python doesn’t require data types to be defined explicitly during variable declarations type errors are likely to occur if the knowledge of data types and their compatibility with each other are neglected. Python provides type() and isinstance() functions to check the type of these variables. These data types can be grouped into the following categories-

  • None Type:Nonekeyword represents the null values in Python. Boolean equality operation can be performed using these NoneType objects.

Class NameDescription

NoneType Represents the NULL values in Python.
  • Numeric Types:There are three distinct numeric types – integers, floating-point numbers, and complex numbers. Additionally, booleans are a sub-type of integers.

Class NameDescription

int Stores integer literals including hex, octal and binary numbers as integers
float Stores literals containing decimal values and/or exponent signs as floating-point numbers
complex Stores complex numbers in the form (A + Bj) and has attributes: real and imag
bool Stores boolean value (True or False).

Note: The standard library also includes fractions to store rational numbers and decimal to store floating-point numbers with user-defined precision.

  • Sequence Types:According to Python Docs, there are three basic Sequence Types – lists, tuples, and range objects. Sequence types have the in and not in operators defined for theirtraversing their elements. These operators share the same priority as the comparison operations.

Class NameDescription

list Mutable sequence used to store collection of items.
tuple Immutable sequence used to store collection of items.
range Represents an immutable sequence of numbers generated during execution.
str Immutable sequence of Unicode code points to store textual data.

Note: The standard library also includes additional types for processing:1. Binary data such as bytearray bytes memoryview , and2. Text strings such as str.

  • Mapping Types:

A mapping object can map hashable values to random objects in Python. Mappings objects are mutable and there is currently only one standard mapping type, the dictionary.

Class Name Description

dict Stores comma-separated list of key: value pairs
  • Set Types:Currently, Python has two built-in set types – set and frozenset. set type is mutable and supports methods like add() and remove(). frozenset type is immutable and can’t be modified after creation.

Class NameDescription

set Mutable unordered collection of distinct hashable objects.
frozenset Immutable collection of distinct hashable objects.

Note:set is mutable and thus cannot be used as key for a dictionary. On the other hand, frozenset is immutable and thus, hashable, and can be used as a dictionary key or as an element of another set.

  • Modules:Module is an additional built-in type supported by the Python Interpreter. It supports one special operation, i.e., attribute access: mymod.myobj, where mymod isa module and myobj references a name defined in m’s symbol table. The module’s symbol table resides in a very special attribute of the module __dict__, but direct assignment to this module is neither possible nor recommended.
  • Callable Types:Callable types are the types to which function call can be applied. They can be user-defined functions, instance methods, generator functions, and some other built-infunctions, methods and classes.Refer to the documentation at docs.python.org for a detailed view of the callable types.
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8. What is pass in Python?

The pass keyword represents a null operation in Python. It is generally used for the purpose of filling upempty blocks of code which may execute during runtime but has yet to be written. Without the pass statement in the following code, we may run into some errors during code execution.

def myEmptyFunc():   # do nothing   passmyEmptyFunc()    # nothing happens## Without the pass keyword# File "<stdin>", line 3# IndentationError: expected an indented block

9. What are modules and packages in Python?

Python packages and Python modules are two mechanisms that allow for modular programming in Python. Modularizing has several advantages –

  • Simplicity: Working on a single module helps you focus on a relatively small portion of the problem at hand. This makes development easier and less error-prone.
  • Maintainability: Modules are designed to enforce logical boundaries between different problem domains. If they are written in a manner that reduces interdependency, it is less likely that modifications in a module might impact other parts of the program.
  • Reusability: Functions defined in a module can be easily reused by other parts of the application.
  • Scoping: Modules typically define a separate namespace, which helps avoid confusion between identifiers from other parts of the program.

Modules, in general, are simply Python files with a .py extension and can have a set of functions, classes, or variables defined and implemented. They can be imported and initialized onceusing the import statement. If partial functionality is needed, import the requisite classes or functions using from foo import bar.

Packages allow for hierarchial structuring of the module namespace using dot notation. As, modules help avoid clashes between global variable names, in a similar manner, packages help avoid clashes between module names.Creating a package is easy since it makes use of the system’s inherent filestructure. So just stuff the modules into a folder and there you have it, the folder name as the package name. Importing a module or its contents from this package requires the package name as prefix to the module name joined by a dot.

Note: You can technically import the package as well, but alas, it doesn’t import the modules within the package to the local namespace, thus, it is practically useless.

10. What are global, protected and private attributes in Python?

  • Global variables are public variables that are defined in the global scope. To use the variable in the global scope inside a function, we use the global keyword.
  • Protected attributes are attributes defined with an underscore prefixed to their identifier eg. _sara. They can still be accessed and modified fromoutside the class they are defined in but a responsible developer should refrain from doing so.
  • Private attributes are attributes with double underscore prefixed to their identifier eg. __ansh. They cannot be accessed or modified from the outside directly and will result in an AttributeError if such an attempt is made.

11. What is the use of self in Python?

Self is usedto represent the instance of the class. With this keyword, you can access the attributes and methods of the class in python. It binds the attributes with the given arguments. self is used in different places and often thought to be a keyword. But unlike in C++, self is not a keyword in Python.

12. What is __init__?

__init__ is a contructor method in Python and is automatically called to allocate memory when a newobject/instance is created. All classes have a __init__ method associated with them. It helps in distinguishing methods and attributes of a class from local variables.

# class definitionclass Student:   def __init__(self, fname, lname, age, section):       self.firstname = fname       self.lastname = lname       self.age = age       self.section = section# creating a new objectstu1 = Student("Sara", "Ansh", 22, "A2")

13. What is break, continue and pass in Python?

BreakContinuePass

The break statement terminates the loop immediately and the control flows to the statement after the body of the loop.
The continue statement terminates the current iteration of the statement, skips the rest of the code in the current iteration and the control flows to the next iteration of the loop.
As explained above, the pass keyword in Python is generally used to fill up empty blocks and is similar to an empty statement represented by a semi-colon in languages such as Java, C++, Javascript, etc.
pat = [1, 3, 2, 1, 2, 3, 1, , 1, 3]for p in pat:   pass   if (p == ):       current = p       break   elif (p % 2 == ):       continue   print(p)    # output => 1 3 1 3 1print(current)    # output => 0

14. What are unit tests in Python?

  • Unit test is a unit testing framework of Python.
  • Unit testing means testing different components of software separately. Can you think about why unit testing is important? Imagine a scenario, you are building software that uses three components namely A, B, and C. Now, suppose your software breaks at a point time. How will you findwhich component was responsible for breaking the software? Maybe it was component A that failed, which in turn failed component B, and this actually failed the software. There can be many such combinations.
  • This is why it is necessary to test each and every component properly so that we know which component might be highly responsible for the failure of the software.

15. What is docstring in Python?

  • Documentationstring or docstring is a multiline string used to document a specific code segment.
  • The docstring should describe what the function or method does.

16. What is slicing in Python?

  • As the name suggests, ‘slicing’ is taking parts of.
  • Syntax for slicing is [start : stop : step]
  • start is the starting index from where to slice a list or tuple
  • stop is the ending index or where to sop.
  • step is the number of steps to jump.
  • Default value for start is 0, stop is number of items, step is 1.
  • Slicing can be done on strings, arrays, lists, and tuples.
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]print(numbers[1 : : 2])  #output : [2, 4, 6, 8, 10]

17. Explain how can you make a Python Scriptexecutable on Unix?

  • Script file must begin with #!/usr/bin/env python

18. What is the difference between Python Arrays and lists?

  • Arrays in python can only contain elements of same data types i.e., data type of array should be homogeneous. It is a thin wrapper around C language arrays and consumes far less memory than lists.
  • Lists in python can contain elementsof different data types i.e., data type of lists can be heterogeneous. It has the disadvantage of consuming large memory.
import arraya = array.array('i', [1, 2, 3])for i in a:    print(i, end=' ')    #OUTPUT: 1 2 3a = array.array('i', [1, 2, 'string'])    #OUTPUT: TypeError: an integer is required (got type str)a = [1, 2, 'string']for i in a:   print(i, end=' ')    #OUTPUT: 1 2 string

Python Interview Questions for Experienced

19. How is memory managed in Python?

  • Memory management in Python is handled by the Python Memory Manager. The memory allocated by the manager is in form of a private heapspace dedicated to Python. All Python objects are stored in this heap and being private, it is inaccessible to the programmer. Though, python does provide some core API functions to work upon the private heap space.
  • Additionally, Python has an in-built garbage collection to recycle the unused memory for the private heap space.

20. What are Python namespaces? Why are they used?

A namespace in Pythonensures that object names in a program are unique and can be used without any conflict. Python implements these namespaces as dictionaries with ‘name as key’ mapped to a corresponding ‘object as value’. This allows for multiple namespaces to use the same name and map it to a separate object. A few examples of namespaces are as follows:

  • Local Namespace includes local names inside a function. the namespace is temporarily created for a function call and gets clearedwhen the function returns.
  • Global Namespace includes names from various imported packages/ modules that are being used in the current project. This namespace is created when the package is imported in the script and lasts until the execution of the script.
  • Built-in Namespace includes built-in functions of core Python and built-in names for various types of exceptions.

The lifecycle of a namespace depends upon thescope of objects they are mapped to. If the scope of an object ends, the lifecycle of that namespace comes to an end. Hence, it isn’t possible to access inner namespace objects from an outer namespace.

21. What is Scope Resolution in Python?

Sometimes objects within the same scope have the same name but functiondifferently. In such cases, scope resolution comes into play in Python automatically. A few examples of such behavior are:

  • Python modules namely ‘math’ and ‘cmath’ have a lot of functions that are common to both of them – log10(), acos(), exp() etc. To resolve this ambiguity, it is necessary to prefix them with their respective module, like math.exp() and cmath.exp().
  • Consider the code below, an object temp has been initialized to 10 globally and then to 20 on function call.However, the function call didn’t change the value of the temp globally. Here, we can observe that Python draws a clear line between global and local variables, treating their namespaces as separate identities.
temp = 10   # global-scope variabledef func():     temp = 20   # local-scope variable     print(temp)print(temp)   # output => 10func()    # output => 20print(temp)   # output => 10

This behavior can be overridden using the global keyword inside the function, as shown in the following example:

temp = 10   # global-scope variabledef func():     global temp     temp = 20   # local-scope variable     print(temp)print(temp)   # output => 10func()    # output => 20print(temp)   # output => 20

22. What are decorators in Python?

Decoratorsin Python are essentially functions that add functionality to an existing function in Python without changing the structure of the function itself. They are represented the @decorator_name in Python and are called in a bottom-up fashion. For example:

# decorator function to convert to lowercasedef lowercase_decorator(function):   def wrapper():       func = function()       string_lowercase = func.lower()       return string_lowercase   return wrapper# decorator function to split wordsdef splitter_decorator(function):   def wrapper():       func = function()       string_split = func.split()       return string_split   return wrapper@splitter_decorator # this is executed next@lowercase_decorator # this is executed firstdef hello():   return 'Hello World'hello()   # output => [ 'hello' , 'world' ]

The beauty of the decorators lies in the fact that besides adding functionality to the output of the method, they can even accept arguments for functions and can further modify those arguments before passing it to the functionitself. The inner nested function, i.e. ‘wrapper’ function, plays a significant role here. It is implemented to enforce encapsulation and thus, keep itself hidden from the global scope.

# decorator function to capitalize namesdef names_decorator(function):   def wrapper(arg1, arg2):       arg1 = arg1.capitalize()       arg2 = arg2.capitalize()       string_hello = function(arg1, arg2)       return string_hello   return wrapper@names_decoratordef say_hello(name1, name2):   return 'Hello ' + name1 + '! Hello ' + name2 + '!'say_hello('sara', 'ansh')   # output => 'Hello Sara! Hello Ansh!'

23. What are Dict and List comprehensions?

Python comprehensions, like decorators, are syntactic sugar constructs that help build altered andfiltered lists, dictionaries, or sets from a given list, dictionary, or set. Using comprehensions saves a lot of time and code that might be considerably more verbose (containing more lines of code). Let’s check out some examples, where comprehensions can be truly beneficial:

  • Performing mathematical operations on the entire list
my_list = [2, 3, 5, 7, 11]squared_list = [x**2 for x in my_list]    # list comprehension# output => [4 , 9 , 25 , 49 , 121]squared_dict = {x:x**2 for x in my_list}    # dict comprehension# output => {11: 121, 2: 4 , 3: 9 , 5: 25 , 7: 49}
  • Performing conditional filtering operations on the entire list
my_list = [2, 3, 5, 7, 11]squared_list = [x**2 for x in my_list if x%2 != ]    # list comprehension# output => [9 , 25 , 49 , 121]squared_dict = {x:x**2 for x in my_list if x%2 != }    # dict comprehension# output => {11: 121, 3: 9 , 5: 25 , 7: 49}
  • Combining multiple lists into one

Comprehensions allow for multiple iterators and hence, can be used to combine multiple lists into one. 

a = [1, 2, 3]b = [7, 8, 9][(x + y) for (x,y) in zip(a,b)]  # parallel iterators# output => [8, 10, 12][(x,y) for x in a for y in b]    # nested iterators# output => [(1, 7), (1, 8), (1, 9), (2, 7), (2, 8), (2, 9), (3, 7), (3, 8), (3, 9)] 
  • Flattening a multi-dimensional list

A similar approach of nested iterators (as above) can be applied to flatten a multi-dimensional list or work upon its inner elements. 

my_list = [[10,20,30],[40,50,60],[70,80,90]]flattened = [x for temp in my_list for x in temp]# output => [10, 20, 30, 40, 50, 60, 70, 80, 90]

Note: List comprehensions have the same effect as the mapmethod in other languages. They follow the mathematical set builder notation rather than map and filter functions in Python.

24. What is lambda in Python? Why is it used?

Lambda is an anonymous function in Python, that can accept any number of arguments, but can only have a single expression. It is generally used in situations requiring an anonymous function for a short timeperiod. Lambda functions can be used in either of the two ways:

  • Assigning lambda functions to a variable:
mul = lambda a, b : a * bprint(mul(2, 5))    # output => 10
  • Wrapping lambda functions inside another function:
def myWrapper(n): return lambda a : a * nmulFive = myWrapper(5)print(mulFive(2))    # output => 10

25. How do you copy an object in Python?

In Python, the assignment statement (= operator) does not copy objects. Instead, it creates a binding between the existing object and the target variable name. To createcopies of an object in Python, we need to use the copy module. Moreover, there are two ways of creating copies for the given object using the copy module –

Shallow Copy is a bit-wise copy of an object. The copied object created has an exact copy of the values in the original object. If either of the values is a reference to other objects, just the reference addresses for the same are copied.Deep Copy copies all valuesrecursively from source to target object, i.e. it even duplicates the objects referenced by the source object.

from copy import copy, deepcopylist_1 = [1, 2, [3, 5], 4]## shallow copylist_2 = copy(list_1) list_2[3] = 7list_2[2].append(6)list_2    # output => [1, 2, [3, 5, 6], 7]list_1    # output => [1, 2, [3, 5, 6], 4]## deep copylist_3 = deepcopy(list_1)list_3[3] = 8list_3[2].append(7)list_3    # output => [1, 2, [3, 5, 6, 7], 8]list_1    # output => [1, 2, [3, 5, 6], 4]

26. What is the difference between xrange and range in Python?

xrange() and range() are quite similar in terms of functionality. They both generate a sequence of integers, with the only difference that range() returns a Python list, whereas, xrange()returns an xrange object.

So how does that make a difference? It sure does, because unlike range(), xrange() doesn’t generate a static list, it creates the value on the go. This technique is commonly used with an object-type generator and has been termed as “yielding“.

Yielding is crucial in applications where memory is a constraint. Creating a static list as in range() can lead to a Memory Error in suchconditions, while, xrange() can handle it optimally by using just enough memory for the generator (significantly less in comparison).

for i in xrange(10):    # numbers from o to 9   print i       # output => 0 1 2 3 4 5 6 7 8 9for i in xrange(1,10):    # numbers from 1 to 9   print i       # output => 1 2 3 4 5 6 7 8 9for i in xrange(1, 10, 2):    # skip by two for next   print i       # output => 1 3 5 7 9

Note: xrange has been deprecated as of Python 3.x. Now range does exactly the same as what xrange used to do in Python 2.x, since it was way better to use xrange() than the original range() function in Python 2.x.

27. What is pickling and unpickling?

Python library offers a feature – serialization out of the box. Serializing an object refers to transforming it into a format that can be stored, so as to be able to deserialize it, later on, to obtain the original object. Here, the pickle module comes into play.

Pickling:

  • Pickling is the name of the serialization process in Python.Any object in Python can be serialized into a byte stream and dumped as a file in the memory. The process of pickling is compact but pickle objects can be compressed further. Moreover, pickle keeps track of the objects it has serialized and the serialization is portable across versions.
  • The function used for the above process is pickle.dump().

Unpickling:

  • Unpickling is the complete inverse of pickling. It deserializes the byte stream to recreate theobjects stored in the file and loads the object to memory.
  • The function used for the above process is pickle.load().

Note: Python has another, more primitive, serialization module called marshall, which exists primarily to support .pyc files in Python and differs significantly from the pickle.

28. What are generators in Python?

Generators are functions that return an iterable collection of items, one at a time, in a setmanner. Generators, in general, are used to create iterators with a different approach. They employ the use of yield keyword rather than return to return a generator object.Let’s try and build a generator for fibonacci numbers –

## generate fibonacci numbers upto ndef fib(n):   p, q = , 1   while(p < n):       yield p       p, q = q, p + qx = fib(10)    # create generator object  ## iterating using __next__(), for Python2, use next()x.__next__()    # output => 0x.__next__()    # output => 1x.__next__()    # output => 1x.__next__()    # output => 2x.__next__()    # output => 3x.__next__()    # output => 5x.__next__()    # output => 8x.__next__()    # error ## iterating using loopfor i in fib(10):   print(i)    # output => 0 1 1 2 3 5 8

29. What is PYTHONPATH in Python?

PYTHONPATH is an environment variable which you can set to add additional directories where Python will look for modules andpackages. This is especially useful in maintaining Python libraries that you do not wish to install in the global default location.

30. What is the use of help() and dir() functions?

help() function in Python is used to display the documentation of modules, classes, functions, keywords, etc. If no parameter is passed to the help() function, then an interactive helputility is launched on the console.dir() function tries to return a valid list of attributes and methods of the object it is called upon. It behaves differently with different objects, as it aims to produce the most relevant data, rather than the complete information.

  • For Modules/Library objects, it returns a list of all attributes, contained in that module.
  • For Class Objects, it returns a list of all valid attributes and base attributes.
  • Withno arguments passed, it returns a list of attributes in the current scope.

31. What is the difference between .py and .pyc files?

  • .py files contain the source code of a program. Whereas, .pyc file contains the bytecode of your program. We get bytecode after compilation of .py file (source code). .pyc files are not created for all the files that you run. It is only createdfor the files that you import.
  • Before executing a python program python interpreter checks for the compiled files. If the file is present, the virtual machine executes it. If not found, it checks for .py file. If found, compiles it to .pyc file and then python virtual machine executes it.
  • Having .pyc file saves you the compilation time.
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32. How Python is interpreted?

  • Python as a languageis not interpreted or compiled. Interpreted or compiled is the property of the implementation. Python is a bytecode(set of interpreter readable instructions) interpreted generally.
  • Source code is a file with .py extension.
  • Python compiles the source code to a set of instructions for a virtual machine. The Python interpreter is an implementation of that virtual machine. This intermediate format is called “bytecode”.
  • .py source code is first compiled to give .pyc which isbytecode. This bytecode can be then interpreted by the official CPython or JIT(Just in Time compiler) compiled by PyPy.

33. How are arguments passed by value or by reference in python?

  • Pass by value: Copy of the actual object is passed. Changing the value of the copy of the object will not change the value of the original object.
  • Passby reference: Reference to the actual object is passed. Changing the value of the new object will change the value of the original object.

In Python, arguments are passed by reference, i.e., reference to the actual object is passed.

def appendNumber(arr):   arr.append(4)arr = [1, 2, 3]print(arr)  #Output: => [1, 2, 3]appendNumber(arr)print(arr)  #Output: => [1, 2, 3, 4]

34. What are iterators in Python?

  • An iterator is an object.
  • It remembers its state i.e., where it is during iteration (see code below to see how)
  • __iter__() method initializes an iterator.
  • It has a __next__() method which returns the next item in iteration and points to the next element. Upon reaching the end of iterable object __next__() must return StopIteration exception.
  • It is also self-iterable.
  • Iterators are objects with which we can iterate over iterable objects like lists, strings, etc.
class ArrayList:   def __init__(self, number_list):       self.numbers = number_list   def __iter__(self):       self.pos =        return self   def __next__(self):       if(self.pos < len(self.numbers)):           self.pos += 1           return self.numbers[self.pos - 1]       else:           raise StopIterationarray_obj = ArrayList([1, 2, 3])it = iter(array_obj)print(next(it)) #output: 2print(next(it)) #output: 3print(next(it))#Throws Exception#Traceback (most recent call last):#...#StopIteration

35. Explain how to delete a filein Python?

Use command os.remove(file_name)

import osos.remove("ChangedFile.csv")print("File Removed!")

36. Explain split() and join() functions in Python?

  • You can use split() function to split a string based on a delimiter to a list of strings.
  • You can use join() function to join a list of strings based on a delimiter to give a single string.
string = "This is a string."string_list = string.split(' ') #delimiter is ‘space’ character or ‘ ‘print(string_list) #output: ['This', 'is', 'a', 'string.']print(' '.join(string_list)) #output: This is a string.

37. What does *args and **kwargs mean?

*args

  • *args is a special syntax used in the function definition to pass variable-length arguments.
  • “*” means variable length and “args” is the name used by convention. You can use any other.
def multiply(a, b, *argv):   mul = a * b   for num in argv:       mul *= num   return mulprint(multiply(1, 2, 3, 4, 5)) #output: 120

**kwargs

  • **kwargs is a special syntax used in the function definition to pass variable-length keyworded arguments.
  • Here,also, “kwargs” is used just by convention. You can use any other name.
  • Keyworded argument means a variable that has a name when passed to a function.
  • It is actually a dictionary of the variable names and its value.
def tellArguments(**kwargs):   for key, value in kwargs.items():       print(key + ": " + value)tellArguments(arg1 = "argument 1", arg2 = "argument 2", arg3 = "argument 3")#output:# arg1: argument 1# arg2: argument 2# arg3: argument 3

38. What are negative indexes and why are they used?

  • Negative indexes are the indexes from the end of the list or tuple or string.
  • Arr[-1] means the last element of array Arr[]
arr = [1, 2, 3, 4, 5, 6]#get the last elementprint(arr[-1]) #output 6#get the second last elementprint(arr[-2]) #output 5

39. How do you create a class in Python?

To create a class in python, we use the keyword “class” as shown in the example below:

class InterviewbitEmployee:   def __init__(self, emp_name):       self.emp_name = emp_name

To instantiate or create an object from the class created above, we do the following:

emp_1=InterviewbitEmployee("Mr. Employee")

To access the name attribute, we just call theattribute using the dot operator as shown below:

print(emp_1.emp_name)# Prints Mr. Employee

To create methods inside the class, we include the methods under the scope of the class as shown below:

class InterviewbitEmployee:   def __init__(self, emp_name):       self.emp_name = emp_name          def introduce(self):       print("Hello I am " + self.emp_name)

The self parameter in the init and introduce functions represent the reference to the current class instance which is used for accessing attributes and methods of that class. The self parameter has to be the first parameter of any method defined inside the class. The method of the class InterviewbitEmployee can beaccessed as shown below:

emp_1.introduce()

The overall program would look like this:

class InterviewbitEmployee:   def __init__(self, emp_name):       self.emp_name = emp_name          def introduce(self):       print("Hello I am " + self.emp_name)       # create an object of InterviewbitEmployee classemp_1 = InterviewbitEmployee("Mr Employee")print(emp_1.emp_name)    #print employee nameemp_1.introduce()        #introduce the employee

40. How does inheritance work in python? Explain it with an example.

A class has the ability to access all the attributes and methods of another class thanks to inheritance. It promotes code reuse and makes application maintenance simpler for developers by preventing the use of unnecessary code. A derived class, also referred to as a child class, is one that derives from another class. The parent class or superclass is the class from which a child class derives its members.

Python supports different kinds of inheritance, they are:

  • Single Inheritance: Child class derives members of one parent class.
# Parent classclass ParentClass:    def par_func(self):         print("I am parent class function")# Child classclass ChildClass(ParentClass):    def child_func(self):         print("I am child class function")# Driver codeobj1 = ChildClass()obj1.par_func()obj1.child_func()
  • Multi-level Inheritance: The members of the parent class, A, are inherited by child class which is then inherited by another child class, B. The features of thebase class and the derived class are further inherited into the new derived class, C. Here, A is the grandfather class of class C.
# Parent classclass A:   def __init__(self, a_name):       self.a_name = a_name   # Intermediate classclass B(A):   def __init__(self, b_name, a_name):       self.b_name = b_name       # invoke constructor of class A       A.__init__(self, a_name)# Child classclass C(B):   def __init__(self,c_name, b_name, a_name):       self.c_name = c_name       # invoke constructor of class B       B.__init__(self, b_name, a_name)          def display_names(self):       print("A name : ", self.a_name)       print("B name : ", self.b_name)       print("C name : ", self.c_name)#  Driver codeobj1 = C('child', 'intermediate', 'parent')print(obj1.a_name)obj1.display_names() 
  • Multiple Inheritance: This is achieved when one child class derives members from more than one parent class. All features of parent classes are inherited in the child class.
# Parent class1class Parent1:   def parent1_func(self):       print("Hi I am first Parent")# Parent class2class Parent2:   def parent2_func(self):       print("Hi I am second Parent")# Child classclass Child(Parent1, Parent2):   def child_func(self):       self.parent1_func()       self.parent2_func()# Driver's codeobj1 = Child()obj1.child_func()
  • Hierarchical Inheritance: When a parent class is derived by more than one child class, it is called hierarchical inheritance.
# Base classclass A:     def a_func(self):         print("I am from the parent class.")# 1st Derived classclass B(A):     def b_func(self):         print("I am from the first child.")# 2nd Derived classclass C(A):     def c_func(self):         print("I am from the second child.") # Driver's codeobj1 = B()obj2 = C()obj1.a_func()obj1.b_func()    #child 1 methodobj2.a_func()obj2.c_func()    #child 2 method

41. How do you access parent members in the child class?

Followingare the ways using which you can access parent class members within a child class:

  • By using Parent class name: You can use the name of the parent class to access the attributes as shown in the example below:
class Parent(object):     # Constructor   def __init__(self, name):       self.name = name     class Child(Parent):    # Constructor   def __init__(self, name, age):       Parent.name = name       self.age = age    def display(self):       print(Parent.name, self.age) # Driver Codeobj = Child("Interviewbit", 6)obj.display()
  • By using super(): The parent class members can be accessed in child class using the super keyword.
class Parent(object):   # Constructor   def __init__(self, name):       self.name = name     class Child(Parent):   # Constructor   def __init__(self, name, age):                '''        In Python 3.x, we can also use super().__init__(name)       '''        super(Child, self).__init__(name)       self.age = age    def display(self):      # Note that Parent.name cant be used       # here since super() is used in the constructor      print(self.name, self.age)  # Driver Codeobj = Child("Interviewbit", 6)obj.display()

42. Are access specifiers usedin python?

Python does not make use of access specifiers specifically like private, public, protected, etc However, it does not derive this from any variables It has the concept of imitating the behaviour of variables by making use of a single (protected) or double underscore (private) as prefixed to the variable names By default, the variables without prefixed underscores are public

Example:

# to demonstrate access specifiersclass InterviewbitEmployee:       # protected members    _emp_name = None    _age = None        # private members    __branch = None        # constructor    def __init__(self, emp_name, age, branch):          self._emp_name = emp_name         self._age = age         self.__branch = branch        #public member    def display():        print(self._emp_name +" "+self._age+" "+self.__branch)

43. Is it possible to call parent class without its instance creation?

Yes, it is possible if the base class is instantiated by other child classes or if the base class is a static method.

44. How is an empty class created in python?

An empty class does not have any members defined in it. It is created by using thepass keyword (the pass command does nothing in python). We can create objects for this class outside the class.For example-

class EmptyClassDemo:   passobj=EmptyClassDemo()obj.name="Interviewbit"print("Name created= ",obj.name)

Output:Name created = Interviewbit

45. Differentiate between new and override modifiers.

The new modifier is used to instruct the compiler to use the new implementation and not the base class function. The Override modifier is useful foroverriding a base class function inside the child class.

46. Why is finalize used?

Finalize method is used for freeing up the unmanaged resources and clean up before the garbage collection method is invoked. This helps in performing memory management tasks.

47. What is init method in python?

The init methodworks similarly to the constructors in Java. The method is run as soon as an object is instantiated. It is useful for initializing any attributes or default behaviour of the object at the time of instantiation.For example:

class InterviewbitEmployee:   # init method / constructor   def __init__(self, emp_name):       self.emp_name = emp_name   # introduce method   def introduce(self):       print('Hello, I am ', self.emp_name)emp = InterviewbitEmployee('Mr Employee')    # __init__ method is called here and initializes the object name with "Mr Employee"emp.introduce()

48. How will you check if a class is a child of another class?

This is done by using a method called issubclass() provided by python.The method tells us if any class is a child of another class by returning true or false accordingly.For example:

class Parent(object):   pass    class Child(Parent):   pass    # Driver Codeprint(issubclass(Child, Parent))    #Trueprint(issubclass(Parent, Child))    #False
  • We can check if an object is an instance of a class by making use of isinstance() method:
obj1 = Child()obj2 = Parent()print(isinstance(obj2, Child))    #False print(isinstance(obj2, Parent))   #True 

Python Pandas Interview Questions

49. What do you know about pandas?

  • Pandas is an open-source, python-basedlibrary used in data manipulation applications requiring high performance. The name is derived from “Panel Data” having multidimensional data. This was developed in 2008 by Wes McKinney and was developed for data analysis.
  • Pandas are useful in performing 5 major steps of data analysis – Load the data, clean/manipulate it, prepare it, model it, and analyze the data.

50. Define pandas dataframe.

Adataframe is a 2D mutable and tabular structure for representing data labelled with axes – rows and columns.The syntax for creating dataframe:

import pandas as pddataframe = pd.DataFrame( data, index, columns, dtype)

where:

  • data – Represents various forms like series, map, ndarray, lists, dict etc.
  • index – Optional argument that represents an index to row labels.
  • columns – Optional argument for column labels.
  • Dtype – the data type of each column. Again optional.

51. How will you combine different pandas dataframes?

The dataframes can be combines using the below approaches:

  • append() method: This is used to stack the dataframes horizontally. Syntax:
df1.append(df2)
  • concat() method: This is used to stack dataframes vertically. This is best used when the dataframes have the same columns and similar fields. Syntax:
pd.concat([df1, df2]) 
  • join()method: This is used for extracting data from various dataframes having one or more common columns.
df1.join(df2)

52. Can you create a series from the dictionary object in pandas?

One dimensional array capable of storing different data types is called a series. We can create pandas series from a dictionary object as shown below:

import pandas as pd    dict_info = {'key1' : 2.0, 'key2' : 3.1, 'key3' : 2.2}  series_obj = pd.Series(dict_info)    print (series_obj)    Output:x     2.0y     3.1z     2.2dtype: float64

If an index is not specified in the input method,then the keys of the dictionaries are sorted in ascending order for constructing the index. In case the index is passed, then values of the index label will be extracted from the dictionary.

53. How will you identify and deal with missing values in a dataframe?

We can identify if a dataframe has missing values by using the isnull() and isna() methods.

missing_data_count=df.isnull().sum()

We can handlemissing values by either replacing the values in the column with 0 as follows:

df[‘column_name’].fillna()

Or by replacing it with the mean value of the column

df[‘column_name’] = df[‘column_name’].fillna((df[‘column_name’].mean()))

54. What do you understand by reindexing in pandas?

Reindexing is the process of conforming a dataframe to a new index with optional filling logic. If the values are missing in the previous index, then NaN/NA is placed in the location. A new object is returnedunless a new index is produced that is equivalent to the current one. The copy value is set to False. This is also used for changing the index of rows and columns in the dataframe.

55. How to add new column to pandas dataframe?

A new column can be added to a pandas dataframe as follows:

import pandas as pd      data_info = {'first' : pd.Series([1, 2, 3], index=['a', 'b', 'c']),           'second' : pd.Series([1, 2, 3, 4], index=['a', 'b', 'c', 'd'])}      df = pd.DataFrame(data_info)    #To add new column thirddf['third']=pd.Series([10,20,30],index=['a','b','c'])    print (df)    #To add new column fourthdf['fourth']=df['first']+info['third']    print (df)    

56.How will you delete indices, rows and columns from a dataframe?

To delete an Index:

  • Execute del df.index.name for removing the index by name.
  • Alternatively, the df.index.name can be assigned to None.
  • For example, if you have the below dataframe:
                Column 1   Names                John               1   Jack               2   Judy               3   Jim                4
  • To drop the index name “Names”:
df.index.name = None# Or run the below:# del df.index.nameprint(df)        Column 1John          1Jack          2Judy          3Jim           4

To delete row/column from dataframe:

  • drop() method is used to delete row/column from dataframe.
  • The axis argument is passed to the drop method where if the value is 0, it indicates to drop/delete a row and if 1 it has to drop the column.
  • Additionally, we can try to delete the rows/columns in place by setting the value of inplace to True. This makes sure that the job is done without the need for reassignment.
  • The duplicate values from the row/column can be deleted by using the drop_duplicates() method.

57. Can you get items of series A that are not available inanother series B?

This can be achieved by using the ~ (not/negation symbol) and isin() method as shown below.

import pandas as pddf1 = pd.Series([2, 4, 8, 10, 12])df2 = pd.Series([8, 12, 10, 15, 16])df1=df1[~df1.isin(df2)]print(df1)"""Output:0    21    4dtype: int64"""

58. How will you get the items that are not common to both the given series A and B?

This can be done by performing the union of the two series first, then taking their intersection. Then we take the strategy of obtaining union items that are missing from the intersection list.

Thefollowing code demonstrates this:

import pandas as pdimport numpy as npdf1 = pd.Series([2, 4, 5, 8, 10])df2 = pd.Series([8, 10, 13, 15, 17])p_union = pd.Series(np.union1d(df1, df2))  # union of seriesp_intersect = pd.Series(np.intersect1d(df1, df2))  # intersection of seriesunique_elements = p_union[~p_union.isin(p_intersect)]print(unique_elements)"""Output:0     21     42     55    136    157    17dtype: int64"""

59. While importing data from different sources, can the pandas library recognize dates?

Yes, they can, but with some bit of help. We need to add the parse_dates argument while we are reading data from the sources. Consider an example where we read data from a CSV file, we may encounter different date-time formatsthat are not readable by the pandas library. In this case, pandas provide flexibility to build our custom date parser with the help of lambda functions as shown below:

import pandas as pdfrom datetime import datetimedateparser = lambda date_val: datetime.strptime(date_val, '%Y-%m-%d %H:%M:%S')df = pd.read_csv("some_file.csv", parse_dates=['datetime_column'], date_parser=dateparser)

Numpy Interview Questions

60. What do you understand by NumPy?

NumPy is one of the most popular, easy-to-use, versatile, open-source, python-based, general-purpose package that is used for processing arrays. NumPy isshort for NUMerical PYthon. This is very famous for its highly optimized tools that result in high performance and powerful N-Dimensional array processing feature that is designed explicitly to work on complex arrays. Due to its popularity and powerful performance and its flexibility to perform various operations like trigonometric operations, algebraic and statistical computations, it is most commonly used in performing scientific computations and various broadcasting functions. The followingimage shows the applications of NumPy:

61. How are NumPy arrays advantageous over python lists?

  • The list data structure of python is very highly efficient and is capable of performing various functions. But, they have severe limitations when it comes to the computation of vectorized operations which deals with element-wise multiplication and addition. The python lists also require the information regarding the type of every element which results in overhead as type dispatching code gets executes every time any operation is performed on any element. This is where the NumPyarrays come into the picture as all the limitations of python lists are handled in NumPy arrays.
  • Additionally, as the size of the NumPy arrays increases, NumPy becomes around 30x times faster than the Python List. This is because the Numpy arrays are densely packed in the memory due to their homogenous nature. This ensures the memory free up is also faster.

62. What are the steps to create 1D,2D and 3D arrays?

  • 1D array creation:
import numpy as npone_dimensional_list = [1,2,4]one_dimensional_arr = np.array(one_dimensional_list)print("1D array is : ",one_dimensional_arr) 
  • 2D array creation:
import numpy as nptwo_dimensional_list=[[1,2,3],[4,5,6]]two_dimensional_arr = np.array(two_dimensional_list)print("2D array is : ",two_dimensional_arr)
  • 3D array creation:
import numpy as npthree_dimensional_list=[[[1,2,3],[4,5,6],[7,8,9]]]three_dimensional_arr = np.array(three_dimensional_list)print("3D array is : ",three_dimensional_arr) 
  • ND array creation: This can be achieved by giving the ndmin attribute. The below example demonstrates the creation of a 6D array:
import numpy as npndArray = np.array([1, 2, 3, 4], ndmin=6)print(ndArray)print('Dimensions of array:', ndArray.ndim)

63. You are given a numpy array and a new column as inputs. How will you delete the second column and replace the column with a new column value?

Example:Given array:

[[35 53 63][72 12 22][43 84 56]]

New Column values:

[     20    30    40]

Solution:

import numpy as np#inputsinputArray = np.array([[35,53,63],[72,12,22],[43,84,56]])new_col = np.array([[20,30,40]])# delete 2nd columnarr = np.delete(inputArray , 1, axis = 1)#insert new_col to arrayarr = np.insert(arr , 1, new_col, axis = 1)print (arr) 

64. How will you efficiently load data from a text file?

We can use the methodnumpy.loadtxt() which can automatically read the file’s header and footer lines and the comments if any.

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This method is highly efficient and even if this method feels less efficient, then the data should be represented in a more efficient format such as CSV etc Various alternatives can be considered depending on the version of NumPy used

Following are the file formats that are supported:

  • Text files: These files are generally very slow, huge but portable and arehuman-readable.
  • Raw binary: This file does not have any metadata and is not portable. But they are fast.
  • Pickle: These are borderline slow and portable but depends on the NumPy versions.
  • HDF5: This is known as the High-Powered Kitchen Sink format which supports both PyTables and h5py format.
  • .npy: This is NumPy’s native binary data format which is extremely simple, efficient and portable.

65. How will you read CSV data into an array in NumPy?

This can be achieved by using the genfromtxt() method by setting the delimiter as a comma.

from numpy import genfromtxtcsv_data = genfromtxt('sample_file.csv', delimiter=',')

66. How will you sort the array based on the Nth column?

For example, consider an array arr.

arr = np.array([[8, 3, 2],          [3, 6, 5],          [6, 1, 4]])

Let us try to sort the rows by the 2nd column so that we get:

[[6, 1, 4],[8, 3, 2],[3, 6, 5]]

We can do this by using the sort()method in numpy as:

import numpy as nparr = np.array([[8, 3, 2],          [3, 6, 5],          [6, 1, 4]])#sort the array using np.sortarr = np.sort(arr.view('i8,i8,i8'),       order=['f1'],       axis=).view(np.int)

We can also perform sorting and that too inplace sorting by doing:

arr.view('i8,i8,i8').sort(order=['f1'], axis=)

67. How will you find the nearest value in a given numpy array?

We can use the argmin() method of numpy as shown below:

import numpy as npdef find_nearest_value(arr, value):   arr = np.asarray(arr)   idx = (np.abs(arr - value)).argmin()   return arr[idx]#Driver codearr = np.array([ 0.21169,  0.61391, 0.6341, 0.0131, 0.16541,  0.5645,  0.5742])value = 0.52print(find_nearest_value(arr, value)) # Prints 0.5645

68. How will you reverse the numpy array using one line ofcode?

This can be done as shown in the following:

reversed_array = arr[::-1]

where arr = original given array, reverse_array is the resultant after reversing all elements in the input.

69. How will you find the shape of any given NumPy array?

We can use the shape attribute of the numpy array to find the shape. It returns the shape of the array in terms of row count and column countof the array.

import numpy as nparr_two_dim = np.array([("x1","x2", "x3","x4"),             ("x5","x6", "x7","x8" )])arr_one_dim = np.array([3,2,4,5,6])# find and print shapeprint("2-D Array Shape: ", arr_two_dim.shape)print("1-D Array Shape: ", arr_one_dim.shape)"""Output:2-D Array Shape:  (2, 4)1-D Array Shape:  (5,)"""

Python Libraries Interview Questions

70. Differentiate between a package and a module in python.

One Python file contains the entire module. A module can import other modules (i.e., Python files) as objects. While a package is the folder or directory where various sub-packages and modules are found.

A python module is created by saving a file withthe extension of .py. This file will have classes and functions that are reusable in the code as well as across modules.

A python package is created by following the below steps:

  • Create a directory and give a valid name that represents its operation.
  • Place modules of one kind in this directory.
  • Create __init__.py file in this directory. This lets python know the directory we created is a package. The contents of this package can be imported across differentmodules in other packages to reuse the functionality.

71. What are some of the most commonly used built-in modules in Python?

Python modules are the files having python code which can be functions, variables or classes. These go by .py extension. The most commonly available built-in modules are:

  • os
  • math
  • sys
  • random
  • re
  • datetime
  • JSON

72. What are lambda functions?

Lambda functions are generally inline, anonymous functions represented by a single expression. They are used for creating function objects during runtime. They can accept any number of parameters. They are usually used where functions are required only for a short period. They can be used as:

mul_func = lambda x,y : x*yprint(mul_func(6, 4))# Output: 24

73. How can yougenerate random numbers?

Python provides a module called random using which we can generate random numbers.

  • We have to import a random module and call the random() method as shown below:
    • The random() method generates float values lying between 0 and 1 randomly.
 import random print(random.random())
  • To generate customised random numbers between specified ranges, we can use the randrange() methodSyntax: randrange(beginning, end, step)For example:
import randomprint(random.randrange(5,100,2))

74. Can you easily check if all characters in the given string is alphanumeric?

Utilizing the isalnum() method, which returns true if the string contains only alphanumeric characters, makes this task simple.

For Example –

"abdc1321".isalnum() #Output: True"[email protected]$".isalnum() #Output: False

Another way is to use match() method from the re (regex) module as shown:

import reprint(bool(re.match('[A-Za-z0-9]+$','abdc1321'))) # Output: Trueprint(bool(re.match('[A-Za-z0-9]+$','[email protected]$'))) # Output: False

75. What arethe differences between pickling and unpickling?

Pickling is the process of converting Python objects to binary format. Unpickling, on the other hand, is the process of converting binary form data into Python objects. The pickled items are used to store data on disks or in external memory spaces. The data is returned as unpickled objects so that python processing can be done on them.

Python provides a pickle module for achieving this. Pickling uses the pickle.dump() method to dumppython objects into disks. Unpickling uses the pickle.load() method to get back the data as python objects.

76. Define GIL.

Global Interpreter Lock is known as GIL. By preventing deadlocks, this mutex is used to restrict access to Python objects and promote efficient thread synchronization. GIL facilitates multitasking, not parallel computing. The operation of GIL is shown in the diagram below.

Based on the above diagram, there are three threads. First Thread acquires the GIL first and starts the I/O execution. When the I/O operations are done, thread 1 releases theacquired GIL which is then taken up by the second thread. The process repeats and the GIL are used by different threads alternatively until the threads have completed their execution. The threads not having the GIL lock goes into the waiting state and resumes execution only when it acquires the lock.

77. Define PYTHONPATH.

It is an environment variable used for incorporating additional directories during the import of amodule or a package. PYTHONPATH is used for checking if the imported packages or modules are available in the existing directories. Not just that, the interpreter uses this environment variable to identify which module needs to be loaded.

78. Define PIP.

PIP stands for Python Installer Package. As the name indicates, it is used for installing different python modules. It is a command-line tool providing a seamless interface forinstalling different python modules. It searches over the internet for the package and installs them into the working directory without the need for any interaction with the user. The syntax for this is:

pip install <package_name>

79. Are there any tools for identifying bugs and performing static analysis in python?

Yes, there are tools like PyChecker and Pylint which are used as staticanalysis and linting tools respectively. PyChecker helps find bugs in python source code files and raises alerts for code issues and their complexity. Pylint checks for the module’s coding standards and supports different plugins to enable custom features to meet this requirement.

80. Differentiate between deep and shallow copies.

  • Shallow copy does the task of creating new objects storingreferences of original elements. This does not undergo recursion to create copies of nested objects. It just copies the reference details of nested objects.
  • Deep copy creates an independent and new copy of an object and even copies all the nested objects of the original element recursively.

81. What is main function in python? How do you invoke it?

In the world of programminglanguages, the main is considered as an entry point of execution for a program. But in python, it is known that the interpreter serially interprets the file line-by-line. This means that python does not provide main() function explicitly. But this doesn’t mean that we cannot simulate the execution of main. This can be done by defining user-defined main() function and by using the __name__ property of python file. This __name__ variable is a special built-in variable that points to the nameof the current module. This can be done as shown below:

def main():   print("Hi Interviewbit!")if __name__=="__main__":   main()

Python Programming Examples

82. Write python function which takes a variable number of arguments.

A function that takes variable arguments is called a function prototype. Syntax:

def function_name(*arg_list)

For example:

def func(*var):   for i in var:       print(i)func(1)func(20,1,6)

The * in the function argument represents variablearguments in the function.

83. WAP (Write a program) which takes a sequence of numbers and check if all numbers are unique.

You can do this by converting the list to set by using set() method and comparing the length of this set with the length of the original list. If found equal, return True.

def check_distinct(data_list): if len(data_list) == len(set(data_list)):   return True else:   return False;print(check_distinct([1,6,5,8]))     #Prints Trueprint(check_distinct([2,2,5,5,7,8])) #Prints False

84. Write a program for counting the number of every character of a given text file.

The idea is to use collections and pprint module as shown below:

import collectionsimport pprintwith open("sample_file.txt", 'r') as data: count_data = collections.Counter(data.read().upper()) count_value = pprint.pformat(count_data)print(count_value)

85. Write a program to check and return the pairs of a given array A whose sum value is equal to atarget value N.

This can be done easily by using the phenomenon of hashing. We can use a hash map to check for the current value of the array, x. If the map has the value of (N-x), then there is our pair.

def print_pairs(arr, N):   # hash set   hash_set = set()       for i in range(, len(arr)):       val = N-arr[i]       if (val in hash_set):    #check if N-x is there in set, print the pair           print("Pairs " + str(arr[i]) + ", " + str(val))       hash_set.add(arr[i])# driver codearr = [1, 2, 40, 3, 9, 4]N = 3print_pairs(arr, N)

86. Write a Program to add two integers >0 without using the plus operator.

We can use bitwise operators to achieve this.

def add_nums(num1, num2):   while num2 != :       data = num1 & num2       num1 = num1 ^ num2       num2 = data << 1   return num1print(add_nums(2, 10))

87. Write a Program to solve the given equation assuming that a,b,c,m,n,o are constants:

ax + by = cmx + ny = o

By solving the equation, we get:

a, b, c, m, n, o = 5, 9, 4, 7, 9, 4temp = a*n - b*mif n != :   x = (c*n - b*o) / temp   y = (a*o - m*c) / temp   print(str(x), str(y))

88. Write a Program to match a string that has the letter ‘a’ followed by 4 to 8 ‘b’s.

We can use the remodule of python to perform regex pattern comparison here.

import redef match_text(txt_data):       pattern = 'ab{4,8}'       if re.search(pattern,  txt_data):    #search for pattern in txt_data           return 'Match found'       else:           return('Match not found')print(match_text("abc"))         #prints Match not foundprint(match_text("aabbbbbc"))    #prints Match found

89. Write a Program to convert date from yyyy-mm-dd format to dd-mm-yyyy format.

We can again use the re module to convert the date string as shown below:

import redef transform_date_format(date):   return re.sub(r'(\d{4})-(\d{1,2})-(\d{1,2})', '\\3-\\2-\\1', date)date_input = "2021-08-01"print(transform_date_format(date_input))

You can also use the datetime module as shown below:

from datetime import datetimenew_date = datetime.strptime("2021-08-01", "%Y-%m-%d").strftime("%d:%m:%Y")print(new_data)

90.Write a Program to combine two different dictionaries. While combining, if you find the same keys, you can add the values of these same keys. Output the new dictionary

We can use the Counter method from the collections module

from collections import Counterd1 = {'key1': 50, 'key2': 100, 'key3':200}d2 = {'key1': 200, 'key2': 100, 'key4':300}new_dict = Counter(d1) + Counter(d2)print(new_dict)

91. How will you access the dataset of a publicly shared spreadsheet in CSV format stored in Google Drive?

Wecan use the StringIO module from the io module to read from the Google Drive link and then we can use the pandas library using the obtained data source.

from io import StringIOimport pandascsv_link = "https://docs.google.com/spreadsheets/d/..."data_source = StringIO.StringIO(requests.get(csv_link).content))dataframe = pd.read_csv(data_source)print(dataframe.head())

Conclusion:

In this article, we have seen commonly asked interview questions for a python developer These questions along with regular problem practice sessions will help you crack any python based interviews Over the years, python has gained a lot of popularity amongst the developers community due to its simplicity andability to support powerful computations Due to this, the demand for good python developers is ever-growing Nevertheless, to mention, the perks of being a python developer are really good Along with theoretical knowledge in python, there is an emphasis on the ability to write good quality code as well So, keep learning and keep practicing problems and without a doubt, you can crack any interviews

Important Resources:

  • Python Basic Programs
  • Python MCQ
  • Python Commands
  • Python Developer Resume
  • Python Projects
  • Difference Between Python 2 and 3
  • Python Frameworks
  • Python Documentation
  • Numpy Tutorial
  • Python Vs R
  • Python Vs Javascript
  • Difference Between C and Python
  • Python Vs Java
  • Features of Python
  • Golang vs Python
  • Python Developer Skills

Python MCQ

list1 = [3,4,5,2,1]

list1 = [3,4,5,2,0]

list1 = [3,5,2,1,0]

list1 = [3,4,5,2]

“Hello World”

“World Hello”

“dlroW olleH”

“olleH dlroW”

List is a sequence data type, while tuple is not

Tuples are mutable but lists are immutable.

Lists are not a sequence data type, whereas a tuple is.

Lists are mutable but tuples are immutable.

100000000000000000000

1e+20

100000000000000000000.0

1.0e+20

__init__ is called manually on object creation.

__init__ is a constructor method in Python.

All classes have a __init__ method associated with them

__init__allocates memory for objects.

pickle.save()

pickle.store()

pickle.pickle()

pickle.dump()

__sara__

__ansh

_sara_

ansh__

A dictionary is used in Python to implement namespaces.

Keys in Python namespaces serve as the object’s addresses.

The lifespan of a namespace is influenced by the scope of the objects it is mapped to.

Namespaces ensure that object names in a program are unique

[“s”, “a,” “r,” “a,” “a,” “a,” “n,” “s,” and “h”].

[“s”, “r”, “a”, “s”, “a”, “a”, “n,” and “h”].

[‘sa’, ‘ra’, ‘an’, ‘sh’]

[“sa” “sa” “sn” “sh” “ra” “ra” “rn” “rh” “aa” “aa” “an” “ah” “sa” “sa” “sn” “sh”

Current time.

Current time in milliseconds.

Current time in milliseconds since midnight, January 1, 1970

The amount of time that has passed since January 1, 1970 at midnight (GMT) in milliseconds.

4 8 24

4 4 64

4 8 64

None of the above

(None, True, ‘IB007’)

(‘Mr Employee’, True, ‘IB007’)

(“”, False,‘IB007’)

Runtime error

pd.read_csv(“sample_file.csv”, encoding=‘utf-8’)

pd.read_csv(“sample_file.csv”, compression=‘gzip’)

pd.read_csv(“sample_file.csv”,dialect=‘comma’)

None of the above

df.emptyframe

df.blank

df.isempty

df.empty

np.search(series_data % 5)

np.find(series_data % 5 ==0)

np.argwhere(series_data % 5==0)

np.locate(series_data % 5)

XYZ ABC

XYZ PQR

LMN ABC

LMN PQR

[num for num<0 in list]

[num<0 in list]

[num for num in list if num<0]

[num in list for num<0]

5

Runtime error

Duplicate Key Exception

3

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Additional Question — What are the basic Python questions asked in interview?

What is data type in Python?

Data types are the classification or categorization of knowledge items It represents the type useful that tells what operations are often performed on specific data Since everything is an object in Python programming, data types are classes and variables are instances (object) of those classes

What is OOPs in Python?

In Python, object-oriented Programming (OOPs) is a programming paradigm that uses objects and classes in programming It aims to implement real-world entities like inheritance, polymorphisms, encapsulation, etc

Is TCS work on Python?

Workwise, it’s alright. learned Python, Perl, and database administration. A couple of my mentors were excellent.

What do you know about TCS interview questions?

TCS Technical Interview Question #1: Describe the linked list’s functionality. 2) What are the four fundamental OOPS principles? 3) What is inheritance? 4) How do variables from one class pass to another class? 5) What is polymorphism? 6) What are the various inheritance types?

What is array in Python?

Array is a container which can hold a fix number of items and these items should be of the same type Most of the data structures make use of arrays to implement their algorithms Following are the important terms to understand the concept of Array Element Each item stored in an array is called an element

How do you create a Fibonacci sequence in Python?

Python Program to Print the Fibonacci sequence
Fibonacci sequence:
Step 1: Input the number of values we want to generate the Fibonacci sequence.
Step 2: Initialize the count = 0, n_1 = 0 and n_2 = 1.
Step 3: If the n_terms
Step 4: print “error” as it is not a valid number for series.

What are Python functions?

Code that only executes when called is known as a function. Data that you supply to a function are referred to as parameters. As a result, a function might return data.

What is prime number in Python?

A prime number is any positive integer greater than 1 that is both the number itself and the only factor, which is 1. 2, 3, 5, 7 etc. due to the absence of any other factors, they are prime numbers.

How do you call a function in Python?

After defining a function, we can use it to call other functions, programs, or even the Python prompt. We just need to type the function name and the appropriate parameters to call the function. Paul, please say hello.

What are the 4 types of functions in Python?

The various categories of Python functions are as follows: Python Built-in Functions. Python Recursion Functions lambda functions in Python. User-defined Functions in Python

What are lists in Python?

An ordered sequence of elements that can be changed or modified is known as a list in the Python programming language. An item is any component or value contained within a list. Lists are denoted by values enclosed in square brackets [], much like strings are defined by characters in quotes.

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