Top 26 Python Programming Interview Questions

1. Python Programming Interview Questions

And we’re back with our third series of Python Programming interview questions. Here we have taken some basic Python Interview questions and answers for freshers, advanced Python Interview Questions and Answers for Experienced, Python Developers interview Question and Answer, Python Coding interview questions, Python Scripting Interview questions as well as data structure interview questions. You can First go through the Python Interview Question Part I and Part II Read along to learn something new and out of the blue.
So, let’s start our Python Programming Interview Questions.
The journey of a THOUSAND miles begins with ONE step.



Q.1. What does the following code output?

>>> def extendList(val, list=[]):
      return list
>>> list1 = extendList(10)
>>> list2 = extendList(123,[])
>>> list3 = extendList('a')
>>> list1,list2,list3

Ans. ([10, ‘a’], [123], [10, ‘a’])

You’d expect the output to be something like this:


Well, this is because the list argument does not initialize to its default value ([]) every time we make a call to the function. Once we define the function, it creates a new list. Then, whenever we call it again without a list argument, it uses the same list. This is because it calculates the expressions in the default arguments when we define the function, not when we call it.

Let’s revise the Basis of Python Programming

Q.2. What is a decorator?

Ans. A decorator is a function that adds functionality to another function without modifying it. It wraps another function to add functionality to it. Take an example.

>>> def decor(func):
    def wrap():

return wrap

>>> @decor
def sayhi():
>>> sayhi()




Decorators are an example of metaprogramming, where one part of the code tries to change another. For more on decorators, read Python


2. Basic Python Programming Interview Questions

Below are some Basic Python Programming Interview Questions and answers for freshers.

Q.3. Write a regular expression that will accept an email id. Use the re module.


>>> import re


To brush up on regular expressions, check Regular Expressions in Python.

Q.4. How many arguments can the range() function take?

Ans. The range() function in Python can take up to 3 arguments. Let’s see this one by one.

a. One argument

When we pass only one argument, it takes it as the stop value. Here, the start value is 0, and the step value is +1.

>>> list(range(5))
[0, 1, 2, 3, 4]
>>> list(range(-5))
>>> list(range(0))
[] b. Two arguments
When we pass two arguments, the first one is the start value, and the second is the stop value.

>>> list(range(2,7))
[2, 3, 4, 5, 6]
>>> list(range(7,2))
>>> list(range(-3,4))
[-3, -2, -1, 0, 1, 2, 3]

c. Three arguments

Here, the first argument is the start value, the second is the stop value, and the third is the step value.

>>> list(range(2,9,2))
[2, 4, 6, 8]
>>> list(range(9,2,-1))
[9, 8, 7, 6, 5, 4, 3]

Q.5. Does Python have a switch-case statement?

Ans. In languages like C++, we have something like this:

    case ‘Ayushi’:
    case ‘Megha’:
        cout<<”Hi, user”;

But in Python, we do not have a switch-case statement. Here, you may write a switch function to use. Else, you may use a set of if-elif-else statements. To implement a function for this, we may use a dictionary.

>>> def switch(choice):
       print(switcher.get(choice,'Hi, user'))


>>> switch('Megha')


>>> switch('Ayushi')


>>> switch('Ruchi')

Hi, user

Here, the get() method returns the value of the key. When no key matches, the default value (the second argument) is returned.

Any doubt yet in Python Programming interview Questions. Please Comment.

Q.6. How do you debug a program in Python? Answer in brief.

Ans. To debug a Python program, we use the pdb module. This is the Python debugger; we will discuss it in a tutorial soon. If we start a program using pdb, it will let us step through the code.

Q.7. List some pdb commands.

Some pdb commands include-

<b> — Add breakpoint

<c> — Resume execution

<s> — Debug step by step

<n> — Move to next line

<l> — List source code

<p> — Print an expression

Q.8. What command do we use to debug a Python program?

Ans. To start debugging, we first open the command prompt, and get to the location the file is at.
Microsoft Windows [Version 10.0.16299.248]

(c) 2017 Microsoft Corporation. All rights reserved.

C:\Users\lifei> cd Desktop

Then, we run the following command (for file

C:\Users\lifei\Desktop>python -m pdb
> c:\users\lifei\desktop\<module>()
-> for i in range(5):


Then, we can start debugging.

Q.9. What is a Counter in Python?

Ans. The function Counter() from the module ‘collections’. It counts the number of occurrences of the elements of a container.

>>> from collections import Counter
>>> Counter([1,3,2,1,4,2,1,3,1])

Counter({1: 4, 3: 2, 2: 2, 4: 1})

Python provides us with a range of ways and methods to work with a Counter. Read Python Counter.

Q.10. What is NumPy? Is it better than a list?

Python Programming Interview Questions - Numpy vs List

Python Programming Interview Questions – Numpy vs List

Ans. NumPy, a Python package, has made its place in the world of scientific computing. It can deal with large data sizes, and also has a powerful N-dimensional array object along with a set of advanced functions.

Yes, a NumPy array is better than a Python list. This is in the following ways:

  1. It is more compact.
  2. It is more convenient.
  3. It Is more efficiently.
  4. It is easier to read and write items with NumPy.

Read our latest tutorial on Python NumPy

Q.11. How would you create an empty NumPy array?

Ans. To create an empty array with NumPy, we have two options:

a. Option 1

>>> import numpy
>>> numpy.array([])

array([], dtype=float64)

b. Option 2

>>> numpy.empty(shape=(0,0))

array([], shape=(0, 0), dtype=float64)

Refer Python Libraries

Q.12. What is PEP 8?

Ans. PEP 8 is a coding convention that lets us write more readable code. In other words, it is a set of recommendations.

Q.13. What is pickling and unpickling?

Ans. To create portable serialized representations of Python objects, we have the module ‘pickle’. It accepts a Python object (remember, everything in Python is an object). It then converts it into a string representation and uses the dump() function to dump it into a file. We call this pickling. In contrast, retrieving objects from this stored string representation is termed ‘unpickling’.

Q.14. What is a namespace in Python?

Python Programming Interview Questions and Answers - Python Namespaces

Python Programming Interview Questions and Answers – Python Namespaces

Ans. A namespace is a collection of names. It maps names to corresponding objects. When different namespaces contain objects with the same names, this avoids any name collisions. Internally, a namespace is implemented as a Python dictionary.

On starting the interpreter, it creates a namespace for as long as we don’t exit. We have local namespaces, global namespaces, and a built-in namespace.

Just Follow this link to know more about Python Namespace

Q.15. How would you perform unit-testing on your Python code?

Ans. For this purpose, we have the module unittest in Python. It has the following members:

So Q2 to Q15 were some Basic Python Programming Interview Questions and Answers for

Freshers. Experienced can also refer these Python Interview Questions for revision.

Python Interview Questions

3. Advanced Python Interview Questions and Answers

Below are some Advanced Python Programming Interview Questions For Experienced. I recommend freshers to also refer these interview questions for advanced knowledge.

Q.16. Explain the use of the ‘nonlocal’ keyword in Python.

Ans. First, let’s discuss the local and global scope. By example, a variable defined inside a function is local to that function. Another variable defined outside any other scope is global to the function.

Suppose we have nested functions. We can read a variable in an enclosing scope from inside he inner function, but cannot make a change to it. For that, we must declare it nonlocal inside the function. First, let’s see this without the nonlocal keyword.

>>> def outer():
    def inner():
>>> outer()

>>> def outer():
    def inner():
>>> outer()

Traceback (most recent call last):
File “<pyshell#462>”, line 1, in <module>
File “<pyshell#461>”, line 7, in outer
File “<pyshell#461>”, line 4, in inner

UnboundLocalError: local variable ‘a’ referenced before assignment

So now, let’s try doing this with the ‘nonlocal’ keyword:

>>> def outer():
    def inner():
        nonlocal a


>>> outer()


Q.17. So, then, what is the global keyword?

Ans. Like we saw in the previous question, the global keyword lets us deal with, inside any scope, the global version of a variable.

The problem:

>>> a=7
>>> def func():

The solution:

>>> a=7
>>> def func():
    global a
>>> func()


Q.18. How would you make a Python script executable on Unix?

Ans. For this to happen, two conditions must be met:

  1. The script file’s mode must be executable
  2. The first line must begin with a hash(#). An  example of this will be: #!/usr/local/bin/python

Q.19. What functions or methods will you use to delete a file in Python?

Ans. For this, we may use remove() or unlink().

>>> import os
>>> os.chdir('C:\\Users\\lifei\\Desktop')
>>> os.remove('')

When we go and check our Desktop, the file is gone. Let’s go make it again so we can delete it again using unlink().

>>> os.unlink('')

Both functions are the same, but unlink is the traditional Unix name for it.

Q.20. What are accessors, mutators, and @property?

Ans. What we call getters and setters in languages like Java, we term accessors and mutators in Python. In Java, if we have a user-defined class with a property ‘x’, we have methods like getX() and setX(). In Python, we have @property, which is syntactic sugar for property(). This lets us get and set variables without compromising on the conventions. For a detailed explanation on property, refer to Python property.

Any Doubt yet in Advanced Python Interview Questions and Answers for Experienced? Please Comment.

Q.21. Explain a few methods to implement Functionally Oriented Programming in Python.

Ans. Sometimes, when we want to iterate over a list, a few methods come in handy.

Python Interview Questions - Python Methods

Python Interview Questions – Python Methods

a. filter()

Filter lets us filter in some values based on conditional logic.

>>> list(filter(lambda x:x>5,range(8)))
[6, 7]

b. map()

Map applies a function to every element in an iterable.

>>> list(map(lambda x:x**2,range(8)))
[0, 1, 4, 9, 16, 25, 36, 49]

c. reduce()

Reduce repeatedly reduces a sequence pair-wise until we reach a single value.

>>> from functools import reduce
>>> reduce(lambda x,y:x-y,[1,2,3,4,5])


Q.22. Differentiate between the append() and extend() methods of a list.

Ans. The methods append() and extend() work on lists. While append() adds an element to the end of the list, extend adds another list to the end of a list.

Let’s take two lists.

>>> list1,list2=[1,2,3],[5,6,7,8]

This is how append() works:

>>> list1.append(4)
>>> list1
[1, 2, 3, 4]

And this is how extend() works:

>>> list1.extend(list2)
>>> list1
[1, 2, 3, 4, 5, 6, 7, 8]

Refer Python Lists

Q.23. Consider multiple inheritances here. Suppose class C inherits from classes A and B as class C(A,B). Classes A and B both have their own versions of method func(). If we call func() from an object of class C, which version gets invoked?

Ans. In our article on Multiple Inheritance in Python, we discussed Method Resolution Order (MRO). C does not contain its own version of func(). Since the interpreter searches in a left-to-right fashion, it finds the method in A, and does not go to look for it in B.

Q.24. Which methods/functions do we use to determine the type of instance and inheritance?

Ans. Here, we talk about three methods/functions- type(), isinstance(), and issubclass().

Python Interview Questions - Python Methods

Python Interview Questions – Python Methods/Functions

a. type()

This tells us the type of object we’re working with.

>>> type(3)

<class ‘int’>

>>> type(False)

<class ‘bool’>

>>> type(lambda :print("Hi"))

<class ‘function’>

>>> type(type)

<class ‘type’>

b. isinstance()

This takes in two arguments- a value and a type. If the value is of the kind of the specified type, it returns True. Else, it returns False.

>>> isinstance(3,int)


>>> isinstance((1),tuple)


>>> isinstance((1,),tuple)

c. issubclass()

This takes two classes as arguments. If the first one inherits from the second, it returns True. Else, it returns False.

>>> class A: pass
>>> class B(A): pass
>>> issubclass(B,A)


>>> issubclass(A,B)


Q.25. What do you mean by overriding methods?

Ans. Suppose class B inherits from class A. Both have the method sayhello()- to each, their own version. B overrides the sayhello() of class A. So, when we create an object of class B, it calls the version that class B has.

>>> class A:
    def sayhello(self):
        print("Hello, I'm A")
>>> class B(A):
   def sayhello(self):
       print("Hello, I'm B")
>>> a=A()
>>> b=B()
>>> a.sayhello()

Hello, I’m A

>>> b.sayhello()

Hello, I’m B

Refer this link to know more about Method Overriding in Python

Q.26. What is JSON? Describe in brief how you’d convert JSON data into Python data?

Ans. JSON stands for JavaScript Object Notation. It is a highly popular data format, and it stores data into NoSQL databases. JSON is generally built on the following two structures:

  1. A collection of <name,value> pairs
  2. An ordered list of values.

Python supports JSON parsers. In fact, JSON-based data is internally represented as a dictionary in Python. To convert JSON data into Python data, we use the load() function from the JSON module.

These were the advanced Python Programming Interview Questions.

This was all about the Python Programming Interview Questions and Answers.

4. Conclusion: Python Programming Interview Questions

Again, we discussed a variety of Python Programming Interview Questions and answers. But stay put, folks, this isn’t all. We meet again with another string of questions to guide you to your interview. Comment if you have a query on Python Programming Interview Questions.
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