Python Programming Language Interview Questions

1. Why Is This Important?
Answer: When it comes to Python interview questions, this one may sound a little silly if you’re a seasoned professional, but it’s best to be ready for it with a comprehensive answer. However, if you’re going for an interview straight after graduation, it will make perfect sense to be asked this question. In this scenario, it will also help your cause if you make some comparisons. (Python Programming Language Interview Questions)

2. What is Python good for?
Answer: Python is a high-level general-purpose programming language that can be applied to many different classes of problems.

The language comes with a large standard library that covers areas such as string processing like regular expressions, Unicode, calculating differences between files, Internet protocols like HTTP, FTP, SMTP, XML-RPC, POP, IMAP, CGI programming, software engineering like unit testing, logging, profiling, parsing Python code, and operating system interfaces like system calls, file systems, TCP/IP sockets.

3. Explain what Flask is and its benefits?
Answer: Flask is a web microframework for Python based on “Werkzeug, Jinja2 and good intentions” BSD license. Werkzeug and Jinja2 are two of its dependencies. This means it will have little to no dependencies on external libraries. It makes the framework light while there is a little dependency to update and fewer security bugs.

A session basically allows you to remember information from one request to another. In a flask, a session uses a signed cookie so the user can look at the session contents and modify. The user can modify the session if only it has the secret key Flask.secret_key.

4. What is the purpose of the PYTHONSTARTUP environment variable?
Answer: PYTHONSTARTUP – It contains the path of an initialization file containing Python source code. It is executed every time you start the interpreter. It is named as in Unix and it contains commands that load utilities or modify PYTHONPATH.

5. How will you convert an integer to a hexadecimal string in python?
Answer: Converts an integer to a hexadecimal string.

6. What Is The Statement That Can Be Used In Python If The Program Requires No Action But Requires It Syntactically?
Answer: The pass statement is a null operation. Nothing happens when it executes. You should use “pass” keyword in lowercase. If you write “Pass,” you’ll face an error like “NameError: name Pass is not defined.” Python statements are case sensitive. (Online training institute)

7. What Are Python Iterators?
Answer: Iterators in Python are array-like objects which allow moving on the next element. We use them in traversing a loop, for example, in a “for” loop.
Python library has a no. of iterators. For example, a list is also an iterator and we can start a for loop over it.

8. How is memory managed in Python?
Answer: Memory management in python is managed by Python private heap space. All Python objects and data structures are located in a private heap. The programmer does not have access to this private heap. The python interpreter takes care of this instead.
The allocation of heap space for Python objects is done by Python’s memory manager. The core API gives access to some tools for the programmer to code.
Python also has an inbuilt garbage collector, which recycles all the unused memory and so that it can be made available to the heap space.

9. What is map function in Python?
Answer: map function executes the function given as the first argument on all the elements of the iterable given as the second argument. If the function given takes in more than 1 arguments, then many tables are given. #Follow the link to know more similar functions.

10. What is multithreading? Give an example?
Answer: It means running several different programs at the same time concurrently by invoking multiple threads. Multiple threads within a process refer the data space with the main thread and they can communicate with each other to share information more easily. Threads are light-weight processes and have less memory overhead. Threads can be used just for a quick task like calculating results and also running other processes in the background while the main program is running.

11. What’s the Difference Between a List and a Dictionary?
Answer: A list and a dictionary in Python are essentially different types of data structures. Lists are the most common data types that boast significant flexibility. Lists can be used to store a sequence of objects that are mutable (so they can be modified after they are created).

In Python, you can’t use a list as a “key” for the dictionary (technically you can hash the list first via your own custom hash functions and use that as a key). A Python dictionary is fundamentally an unordered collection of key-value pairs. It’s a perfect tool to work with an enormous amount of data since dictionaries are optimized for retrieving data (but you have to know the key to retrieve its value).

It can also be described as the implementation of a hashtable and as a key-value store. In this scenario, you can quickly look up anything by its key, but since it’s unordered, it will demand that keys are hashes. When you work with Python, dictionaries are defined within curly braces {} where each item will be a pair in the form key: value.

12. Why Is It Important?
Answer: Although this has nothing to do specifically with Python programming interview questions, there’s a good chance that you will have to answer these types of questions. In any position, technical or not, the behavioral aspects of each individual also play a critical in the selection process. This is because even if you’re the best Python programmer in the marketplace, it won’t mean much if you can’t perform efficiently and effectively on the job.

13. What Is the Accomplishment You Are Most Proud Of?
Answer: This interview question is designed to test your storytelling skills in the context of a professional example. So it’s important to start by setting the stage for your example. You can do this by talking about where you were working at the time, the project you were working on, the people you worked with, how you worked (tools, processes, the time is taken), and the specific results.

You will have to think on your feet as there may well be follow-up questions, so be prepared to dive in and get into the nitty-gritty details. It’s essential to use a recent example here, so keep it fresh and give the recruiter a chance to imagine your future success based on your past work experience.

14. When Would You Use a List vs. a Tuple vs. a Set in Python?
Answer: A list is a common data type that is highly flexible. It can store a sequence of objects that are mutable, so it’s ideal for projects that demand the storage of objects that can be changed later.

A tuple is similar to a list in Python, but the key difference between them is that tuples are immutable. They also use less space than lists and can only be used as a key in a dictionary. Tuples are a perfect choice when you want a list of constants.

Sets are a collection of unique elements that are used in Python. Sets are a good option when you want to avoid duplicate elements in your list. This means that whenever you have two lists with common elements between them, you can leverage sets to eliminate them.

15. How many data types are there in Python?
Answer: One of the more common interview questions on Python – you might get asked to either say the number or actually name them.
Python has five different data types: string, list, number, dictionary, and tuple.

16. How will you differentiate between deep copy and shallow copy?
Answer: We use a shallow copy when a new instance type gets created. It keeps the values that are copied in the new instance. Just like it copies the values, the shallow copy also copies the reference pointers.

Reference points copied in the shallow copy reference to the original objects. Any changes made in any member of the class affects the original copy of the same. Shallow copy enables faster execution of the program.

Deep copy is used for storing values that are already copied. Unlike shallow copy, it doesn’t copy the reference pointers to the objects. Deep copy makes the reference to an object in addition to storing the new object that is pointed by some other object.

Changes made to the original copy will not affect any other copy that makes use of the referenced or stored object. Contrary to the shallow copy, a deep copy makes the execution of a program slower. This is due to the fact that it makes some copies for each object that is called.

17. How can you organize your code to make it easier to change the base class?
Answer: You have to define an alias for the base class, assign the real base class to it before your class definition, and use the alias throughout your class. You can also use this method if you want to decide dynamically (e.g., depending on the availability of resources) which base class to use. 

18. What is a negative index in Python?
Answer: Python sequences are accessible using an index in positive and negative numbers. For example, 0 is the first positive index, 1 is the second positive index and so on. For negative indexes -1 is the last negative index, -2 is the second last negative index and so on.

Index traverses from left to right and increases by one until the end of the list.

Negative index traverse from right to left and iterate one by one till the start of the list. A negative index is used to traverse the elements into reverse order.

19. What is slicing in Python?
Answer: Slicing is a mechanism used to select a range of items from sequence type like list, tuple, and string. It is beneficial and easy to get elements from a range by using slice way. It requires a : (colon) which separates the start and end index of the field. All the data collection types List or tuple allows us to use slicing to fetch elements. Although we can get elements by specifying an index, we get only single element whereas using slicing we can get a group of elements.

20. What is a dictionary in Python?
Answer: The Python dictionary is a built-in data type. It defines a one-to-one relationship between keys and values. Dictionaries contain a pair of keys and their corresponding values. It stores elements in key and value pairs. The keys are unique whereas values can be duplicate. The key accesses the dictionary elements.

21. What are the different file processing modes supported by Python?
Answer: Python provides three modes to open files. The read-only, write-only, read-write and append mode. ‘r’ is used to open a file in read-only mode, ‘w’ is used to open a file in write-only mode, ‘rw’ is used to open in reading and write mode, ‘a’ is used to open a file in append mode. If the mode is not specified, by default file opens in read-only mode. 

22. How to overload constructors or methods in Python?
Answer: Python’s constructor: _init__ () is the first method of a class. Whenever we try to instantiate an object __init__() is automatically invoked by python to initialize members of an object. We can’t overload constructors or methods in Python. It shows an error if we try to overload.

23. What is Python Tuples and how is it different from Lists?
Answer: Tuples is basically a sequence of elements which are separated by commas and are enclosed in parenthesis.

Lists whereas is a sequence of elements which are separated by commas and are enclosed in brackets. Also, Tuples cannot be updated whereas, in lists, elements can be updated along with their sizes.

24. How do you launch sub-processes within the main process of a Python application?
Answer: Python has a built-in module called sub-process. You can import this module and either use run() or Popen() function calls to launch a sub-process and get the control of its return code.

25. How do you implement JSON given that Python is best suited for the server-side application?
Answer: Python has built-in support to handle JSON objects.

You just have to import the JSON module and use the functions such as loads and dumps to convert from JSON string to JSON object and vice versa. It is a straightforward way to handle and exchange JSON based data from the server-side.

26. Can Python be used for web client and web server side programming? And which one is best suited to Python?
Answer: Python is best suited for web server-side application development due to its vast set of features for creating business logic, database interactions, web server hosting, etc.

However, Python can be used as a web client-side application which needs some conversions for a browser to interpret the client-side logic. Also, note that Python can be used to create desktop applications which can run as a standalone application such as utilities for test automation.

27. What should be the typical build environment for Python-based application development?
Answer: You just need to install Python software and using PIP, you can install various Python modules from the open source community.

For IDE, Pycharm is highly recommended for any kind of application development with vast support for plugins. Another basic IDE is called a RIDE and is a part of the Python open source community.

28. Explain the interpretation in Python?
Answer: Programs in python run directly from the source code.

29. What are python and name some key features of it?
Answer: Python is an interpreter-based programming language, interactive and object-oriented scripting language. Python is designed to be highly readable.

It is an interpreter based language which means that, unlike other languages like C and variants, the compilation doesn’t require before running.
It’s dynamically typed, which means you need not to define the datatypes of the declared variables and anything like that.
Eg: You can declare variable x=10 and then x=” Hello World” without error it will define the datatype by default depending on its value.

30. What is the Dictionary?

  • Dictionary objects can be created by using curly braces {} or by calling dictionary function
  • Dictionary objects are mutable objects
  • Dictionary represents a key-value base
  • Each key-value pair of Dictionary is known as an item
  • Dictionary keys must be immutable
  • Dictionary values can be mutable or immutable
  • Duplicate keys are not allowed but values can be duplicate
  • Insertion order is not preserved
  • Heterogeneous keys and heterogeneous values are allowed.

30. What Are The Implementation In Python Program?
Answer: Python program can be implemented in two ways

1. Interactive Mode (Submit statement by statement explicitly)
2. Batch Mode (Writing all statements and submit all statements)

In Interactive mode, the python command shell is required. It is available in the installation of python cell.
In Interactive mode is not suitable for developing the projects & Applications
Interactive mode is used for predefined function and programs.

31. How do I test a Python program or component?
Answer: Python comes with two testing frameworks:

The documentation test module finds examples in the documentation strings for a module and runs them, comparing the output with the expected output given in the documentation string.
The unit test modules a fancier testing framework modeled on Java and Smalltalk testing frameworks.

For testing, it helps to write the program so that it may be easily tested by using good modular design. Your program should have almost all functionality encapsulated in either functions or class methods. And this sometimes has the surprising and delightful effect of making the program run faster because local variable accesses are faster than global accesses.

Furthermore, the program should avoid depending on mutating global variables since this makes testing much more difficult to do.
The “global main logic” of your program may be as simple as.

31. How is Python executed?
Answer: Python files are compiled to bytecode. which is then executed by the host.

32. How do you open an already existing file and add content to it?
Answer: In Python, open(,) is used to open a file in different modes. The open function returns a handle to the file, using which one can perform read, write and modify operations.

33. When do you choose a list over a tuple?
Answer: When there is an immutable ordered list of elements we choose tuple. Because we cannot add/remove an element from the tuple. On the other hand, we can add elements to a list using append () or extend() or insert(), etc., and delete elements from a list using remove() or pop().

Simple tuples are immutable, and lists are not. Based on these properties one can decide what to choose in their programming context.

34. What are the generator functions in Python?
Answer: Any function that contains at least one yield statement is called a generator function instead of a return statement. The difference between return and yield is, return statement terminates the function, and yield statement saving all its states pauses and later continues from there on successive calls.

35. How do you invoke the Python interpreter for interactive use?
Answer: python or python.y where x.y is the version of the Python interpreter desired?

36. Why do you need to make your code more readable?
Answer: We need to make our code more readable so that other programmer can understand our code. Basically, for a large project, many programmers work together. So, if the readability of the code is poor, it will be difficult for others to improve the code later.

37. How Python supports encapsulation with respect to functions?
Answer: Python supports inner functions. A function defined inside a function is called an inner function, whose behavior is not hidden. This is how Python supports encapsulation with respect to functions.

38. What is the difference between range() and xrange() functions in Python?
Answer: range() is a function that returns a list of numbers, which will be an overhead if the number is too large. Whereas, xrange() is a generator function that returns an iterator which returns a single generated value whenever it is called.

39. How do you perform pattern matching in Python? Explain?
Answer: Regular Expressions/REs/ regexes enable us to specify expressions that can match specific “parts” of a given string. For instance, we can define a regular expression to match a single character or a digit, a telephone number, or an email address, etc. The Python’s “re” module provides regular expression patterns and was introduce from later versions of Python 2.5. “re” module is providing methods for search text strings, or replacing text strings along with methods for splitting text strings based on the pattern defined.

40. What is the difference between range & xrange? Explain?
Answer: For the most part, xrange and range are the exact same in terms of functionality. They both provide a way to generate a list of integers for you to use, however you please. The only difference is that range returns a Python list object and x range returns an xrange object.

This means that xrange doesn’t actually generate a static list at run-time as the range does. It creates the values as you need them with a special technique called yielding. This technique is used with a type of object known as generators. That means that if you have a really gigantic range you’d like to generate a list for, say one billion, xrange is the function to use.

This is especially true if you have a real memory sensitive system such as a cell phone that you are working with, as the range will use as much memory as it can to create your array of integers, which can result in a Memory Error and crash your program. It’s a memory hungry beast.

41. What is the difference between deep and shallow copy?
Answer: Shallow copy is used when a new instance type gets created and it keeps the values that are copied in the new instance. Shallow copy is used to copy the reference pointers just like it copies the values. These references point to the original objects and the changes made in any member of the class will also affect the original copy of it. Shallow copy allows faster execution of the program and it depends on the size of the data that is used.

Deep copy is used to store the values that are already copied. The deep copy doesn’t copy the reference pointers to the objects. It makes the reference to an object and the new object that is pointed by some other object gets stored. The changes made in the original copy won’t affect any other copy that uses the object. Deep copy makes the execution of the program slower due to making certain copies for each object that is been called.

42. What is the difference between NumPy and SciPy?
Answer: In an ideal world, NumPy would contain nothing but the array data type and the most basic operations: indexing, sorting, reshaping, basic elementwise functions, et cetera.
All numerical code would reside in SciPy. However, one of NumPy’s important goals is compatibility, so NumPy tries to retain all features supported by either of its predecessors.
Thus NumPy contains some linear algebra functions, even though these more properly belong in SciPy. In any case, SciPy contains more fully-featured versions of the linear algebra modules, as well as many other numerical algorithms.
If you are doing scientific computing with python, you should probably install both NumPy and SciPy. Most new features belong in SciPy rather than NumPy.

43. What is the process of compilation and linking in python?
Answer: The compiling and linking allows the new extensions to be compiled properly without any error and the linking can be done only when it passes the compiled procedure. If the dynamic loading is used then it depends on the style that is being provided with the system. The python interpreter can be used to provide the dynamic loading of the configuration setup files and will rebuild the interpreter.

The steps that are required in this as:

Create a file with any name and in any language that is supported by the compiler of your system. For example file.c or file.cpp
Place this file in the Modules/ directory of the distribution which is getting used.
Add a line in the file Setup.local that is present in the Modules/ directory.
Run the file using spam file.o
After successful run of this rebuild the interpreter by using the make command on the top-level directory.
If the file is changed then run rebuildMakefile by using the command as ‘make Makefile’.

44. What is the namespace in Python?
Answer: In Python, every name has a place where it lives. It is known as a namespace. It is like a box where a variable name maps to the object placed. Whenever the variable is searched out, this box will be searched, to get the corresponding object.

45. What are the rules for a local and global variable in Python?
Answer: In Python, variables that are only referenced inside a function are called implicitly global. If a variable is assigned a new value anywhere within the function’s body, it’s assumed to be a local. If a variable is ever assigned a new value inside the function, the variable is implicitly local, and we need to declare it as ‘global’ explicitly. To make a variable globally, we need to declare it by using the global keyword. Local variables are accessible within the local body only. Global variables are accessible anywhere in the program, and any function can access and modify its value.

46. How Python does Compile-time and Run-time code checking?
Answer: In Python, some amount of coding is done at compile-time, but most of the checking such as type, name, etc. are postponed until code execution. Consequently, if the Python code references a user-defined function that does not exist, the code will compile successfully. The Python code will fail only with an exception when the code execution path does not exist.

47. What are the Runtime Errors?
Answer: The errors which occur after starting the execution of the programs are known as runtime errors.
Runtime errors can occur because of

Invalid Input
Invalid Logic
Memory issues
Hardware failures and so on
With respect to every reason which causes to runtime error corresponding runtime error representation class is available

Runtime error representation classes technically we call as an exception class.
While executing the program if any runtime error occurs corresponding runtime error representation class object is created
Creating a runtime error representation class object is technically known as a rising exception
While executing the program if an exception is raised, then internally python interpreter verify any code is implemented to handle the raised exception or not
If a code is not implemented to handle raised exception then the program will be terminated abnormally

48. What is PIP software in the Python world?
Answer: PIP is an acronym for Python Installer Package which provides a seamless interface to install various Python modules. It is a command line tool which can search for packages over the internet and install them without any user interaction.

49. How is Exception Handling done in Python?
Answer: There are 3 main keywords i.e. try, except and finally which are used to catch exceptions and handle the recovering mechanism accordingly. Try is the block of a code which is monitored for errors. Except block gets executed when an error occurs.

The beauty of the final block is to execute the code after trying for error. This block gets executed irrespective of whether an error occurred or not. Finally block is used to do the required cleanup activities of objects/variables.

50. What is an operator in Python?
Answer: An operator is a particular symbol which is used on some values and produces an output as a result. An operator works on operands. Operands are numeric literals or variables which hold some values. Operators can be unary, binary or ternary. An operator which require a single operand known as a unary operator, which require two operands known as a binary operator and which require three operands is called ternary operator.

51. What Is the Biggest Challenge Facing Your Current Job Right Now? What Is Your Biggest Failure?
Answer: This question comes up often regardless of the field because it helps the interviewer get an idea of your approach to problem-solving in your new potential role. The way you approach the answer will make you look awesome, or it will be a red flag. So it will be critical to think about this beforehand and answer the question without delay.

As a rule, don’t complain about the management at your current job or blame the people you’re working with. It’s also not a good idea to pretend like your career has been a walk in the park. Instead, tailor your answer to a project you worked on, but don’t get specific about why the challenge turned out to be difficult in the first place. Instead, concentrate on the problem-solving process to highlight your skills.

When it comes to your biggest failure, it’s critical that you don’t use this time to talk yourself down. If you can’t think of a specific scenario, think of a time when you were disappointed about something that didn’t work out. The primary objective is to show the interviewer how you managed to turn something negative into something positive.

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