Python Programming Interview Questions

31. 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.

32. 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.

33. 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

34. 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. 

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

36. 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. 

37. 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.

38. 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.

39. 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.

40. 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.

41. 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.

42. 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 module is 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.

43. 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.

44. 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.

45. 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.

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

47. 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.

48. 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. 

49. 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.

50. 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.

51. 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.

52. 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 .pythonrc.py in Unix and it contains commands that load utilities or modify PYTHONPATH.

53. 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.

54. As Python is more suitable for the server-side application, it is very important to have threading implemented in your server code. How can you achieve that in Python?
Answer: We should use the threading module to implement, control and destroy threads for parallel execution of the server code. Locks and Semaphores are available as synchronization objects to manage data between different threads.

55. How to remove leading whitespaces from a string in the Python?
Answer: To remove leading characters from a string, we can use strip() function. It is Python string function which takes an optional char type parameter. If a parameter is provided, it removes the character. Otherwise, it removes all the leading spaces from the string.