If you’re preparing for a Python interview, it’s important to familiarize yourself with common interview questions and have a solid understanding of the language.
In this guide, we’ll cover the top interview questions on Python :
What is Python?
Python is a high-level, interpreted programming language known for its simplicity and readability. It was created by Guido van Rossum and first released in 1991.
Python supports object-oriented programming principles, allowing developers to structure their code using classes and objects.
Interview questions on python
Now lets start with pyhton interview questions
Q1.What is Python? Mention its key features.
Ans.Python is a high-level, interpreted programming language known for its simplicity and readability. It was created by Guido van Rossum and first released in 1991. Python is designed to be easy to learn and use, making it a popular choice for beginners and experienced developers alike.The Features are as follows:-
- Python emphasizes code readability with a clean and straightforward syntax that resembles English-like phrases, reducing the cost of program maintenance and development.
- Python code is executed line by line by the Python interpreter, rather than being compiled into machine code like languages such as C or C++.
- Python provides built-in data structures such as lists, dictionaries, tuples, and sets, making it simple to work with complex data and algorithms.
- Python is dynamically typed, meaning you don’t need to specify the data type of a variable explicitly. The data type is inferred at runtime.
- Python supports object-oriented programming principles, allowing developers to structure their code using classes and objects.
- Python comes with a vast standard library that provides modules for various tasks, such as working with files, networking, web development, and more.
- Python is designed to be platform-independent, meaning Python code written on one operating system can be easily run on another without modifications
Q2.How is Python different from other programming languages like Java and C++?
Ans.The difference between java,C++and pyhton are as follows:-
|Syntax and Readability||Python emphasizes a clean and readable syntax with significant indentation||Java has a more verbose syntax compared to Python, with a strong emphasis on object-oriented programming||C++ syntax is also more complex than Python, and it includes pointers, memory management, and other low-level features|
|Interpretation vs. Compilation||Python is an interpreted language||Java is a compiled language||C++ is also a compiled language. The C++ source code is compiled into machine code by a C++ compiler before execution.|
|Application Domains||Python is commonly used for web development, scientific computing, data analysis, machine learning, automation, and scripting tasks.||Java is popular for enterprise-level applications, Android app development, large-scale systems, and server-side applications.||C++ is widely used in system-level programming, game development, performance-critical applications, and embedded systems.|
Q3.Explain the differences between Python 2 and Python 3.
Ans.The major differences between Python 2 and Python 3 are as follows:-
|Python 2: Strings are ASCII by default, and Unicode strings are specified with a u prefix, like u”Hello”||Python 3: Strings are Unicode by default, and byte strings are specified with a b prefix, like b”Hello”.|
|Python 2: The input() function evaluates user input as Python code, which can be a security risk.||Python 3: The input() function behaves like Python 2’s raw_input(), returning the user’s input as a string.|
|Python 2: Dictionary methods dict.keys(), dict.values(), and dict.items() return lists.||Python 3: Dictionary methods dict.keys(), dict.values(), and dict.items() return dictionary view objects.|
Q4.What are the main data types in Python?
Ans.The main data types in python are:
int: Represents integer values, e.g., 42, -123, 0.
float: Represents floating-point values (real numbers with decimal points), e.g., 3.14, -0.5, 2.0.
bool: Represents Boolean values, which can be either True or False.
str: Represents strings of characters, e.g., “Hello, Python!”, ‘123’, “This is a string”.
list: Represents ordered collections of elements, which can be of different data types. Lists are mutable (can be modified after creation).
tuple: Represents ordered collections of elements, similar to lists, but tuples are immutable (cannot be modified after creation).
range: Represents a sequence of numbers, typically used for iteration.
dict: Represents key-value pairs, where each key maps to a value. Dictionaries are also known as associative arrays or hash maps.
set: Represents an unordered collection of unique elements. Sets do not allow duplicate values.
frozenset: Similar to sets, but frozensets are immutable.
None: Represents the absence of a value or a null value in Python
Q5.How do you comment on a single line and multiple lines in Python?
To add a comment on a single line, you can use the # symbol.
Using triple quotes (”’ or “””)
Q6.How do you declare and use variables in Python?
To declare a variable, you simply assign a value to it using the assignment operator (=). The variable name must follow certain rules:
- It must start with a letter (a-z, A-Z) or an underscore (_).
- It can be followed by letters, underscores, and digits (0-9).
- Variable names are case-sensitive.
Once a variable is declared, you can use its value throughout your code. For example, you can use the variable in expressions, print statements, function calls, and so on.For ex:-
# Using variables in expressions
x = 10
y = 20
result = x + y
print(result) # Output: 30
# Using variables in print statements
name = “Alice”
print(“Hello, ” + name) # Output: Hello, Alice
# Using variables in function calls
length = 5
width = 3
area = length * width
print(“The area is:”, area) # Output: The area is: 15
Q7.Explain the concept of indentation in Python.
Ans.Indentation is the number of spaces or tabs at the beginning of a line. The number of spaces or tabs used for indentation should be consistent throughout the code and is usually set to four spaces (PEP 8 recommends using spaces).
Q8.How can you take user input in Python?
Ans.In Python, you can take user input from the keyboard using the built-in input() function. The input() function reads the user’s input as a string and returns the input as a string value.Ex:-
# Taking user input and storing it in a variable
name = input(“Enter your name: “)
Q9.What are reserved words in Python?
Ans.In Python, reserved words, also known as keywords, are a set of words that have special meanings and are reserved for specific purposes within the language. These words cannot be used as identifiers (e.g., variable names, function names) because they are part of Python’s syntax and have predefined meanings.Some reserved words:-
- True, False, and None
- and, or, not
- if, else, elif
- while, for
- break, continue
- def, return
Q10.What is the purpose of the “pass” statement in Python?
Ans.In Python, the pass statement is a null statement, meaning it doesn’t do anything when executed. It is a placeholder that serves a specific purpose in Python syntax. The primary use of the pass statement is to act as a syntactic placeholder where Python requires a statement, but you don’t want to execute any code at that point.
Q11.Explain the “while” loop in Python.
Ans.In Python, the while loop is used to repeatedly execute a block of code as long as a certain condition is true. It allows you to create a loop where the code inside the loop is executed repeatedly until the specified condition evaluates to False. Once the condition becomes False, the loop terminates, and the program continues with the next statement after the loop.Ex:-
Q12.What is the “for” loop used for, and how does it work?
Ans.In Python, the for loop is used to iterate over a sequence (such as a list, tuple, string, or dictionary) and execute a block of code for each item in the sequence.
The for loop simplifies the process of repeatedly executing code for each element in a collection, making it an essential tool for various tasks involving iteration .Ex:-
In Python, the for loop is used to iterate over a sequence (such as a list, tuple, string, or dictionary) and execute a block of code for each item in the sequence.
The for loop simplifies the process of repeatedly executing code for each element in a collection, making it an essential tool for various tasks involving iteration.
example, the for loop iterates over the fruits list, and in each iteration, it assigns the current element to the fruit variable. The code inside the loop (the print(fruit) statement) is executed for each item in the list, printing its value.
fruits = [“apple”, “banana”, “orange”, “grape”]
for fruit in fruits:
Q13.How do you exit a loop prematurely in Python?
Ans.In Python, you can exit a loop prematurely using the break statement. The break statement allows you to immediately exit the loop before it has completed all iterations, based on a certain condition.Ex:-
fruits = [“apple”, “banana”, “orange”, “grape”]
for fruit in fruits:
if fruit == “orange”:
print(“Orange found. Exiting loop.”)
In this example, the for loop iterates over the fruits list, and for each fruit, it checks if the fruit is equal to “orange”. When the condition fruit == “orange” is met, the break statement is executed.
As a result, the loop is terminated prematurely, and the program continues with the next statement after the loop (print(“Orange found. Exiting loop.”)).
Q14.What is the “range” function used for?
Ans.In Python, the range() function is used to generate a sequence of numbers. It is a built-in function that returns an immutable sequence of numbers within a specified range.
The range() function is often used in for loops when you need to iterate over a sequence of numbers.
Q15.Describe the “break” and “continue” statements in Python.
The break statement is used to immediately exit a loop prematurely. When the break statement is encountered inside a loop, the loop is terminated, and the program continues with the next statement after the loop.
The continue statement is used to skip the rest of the current iteration and move on to the next iteration of the loop. When the continue statement is encountered inside a loop, the current iteration’s remaining code is skipped, and the loop proceeds with the next iteration.
Q16.How do you use the “else” clause with loops?
Ans.In Python, you can use the else clause with loops to specify a block of code that should be executed when the loop completes its iterations without encountering a break statement.
The else clause is optional and allows you to handle a specific condition after the loop has finished its normal execution. Ex:-
count = 0
while count < 5:
count += 1
In this example, the while loop runs until count becomes equal to 5. After the loop completes all iterations (when count is no longer less than 5), the else block is executed, and the message “Loop finished.” is printed.
Q17.What is a “list comprehension” in Python?
Ans.A “list comprehension” is a concise and powerful way to create lists in Python. It provides a compact syntax for generating new lists by applying an expression to each item in an existing iterable (e.g., a list, tuple, string, etc.)
Q18.Explain the “try-except” block in Python for exception handling.
Ans.In Python, the try-except block is used for exception handling, allowing you to handle potential errors or exceptions gracefully. When you expect that a certain section of code may raise an exception, you can place that code inside a try block.
If an exception occurs within the try block, it is caught, and the corresponding except block is executed, allowing you to handle the exception and take appropriate actions.
Q19.How can you raise custom exceptions in Python?
Ans.In Python, you can raise custom exceptions to handle specific situations or error conditions in your code. To raise a custom exception, you need to define your own exception class, which is a subclass of the built-in Exception class or any of its subclasses.
By creating custom exceptions, you can provide more meaningful and informative error messages tailored to your application’s needs.
Creating Custom Exception Class:
To create a custom exception, define a new class that inherits from the Exception class or any of its subclasses. It is common to create custom exception classes by subclassing Exception directly. You can also subclass more specific exception classes like ValueError, TypeError, etc., depending on the nature of your custom exception.
Raising Custom Exception:
Once you have defined your custom exception class, you can raise it using the raise statement when a specific condition in your code is met.
Q20.How do you write an if-else statement in Python?
Ans.In Python, an if-else statement is used to conditionally execute different blocks of code based on the evaluation of a specific condition. If the condition is True, the code inside the if block is executed.
If the condition is False, the code inside the else block is executed. The else block is optional, and it provides an alternative set of instructions to execute when the condition is False.Ex:-
num = int(input(“Enter a number: “))
if num % 2 == 0:
print(“The number is even.”)
print(“The number is odd.”)
In this example, the user enters a number, and the program checks whether it is even or odd using the modulo operator (num % 2).
If the remainder is zero (num is even), the code inside the if block is executed, and “The number is even.” is printed. If the remainder is not zero (num is odd), the code inside the else block is executed, and “The number is odd.” is printed.
Q21.Define a function in Python and explain its syntax.
Ans.In Python, a function is a block of organized, reusable code that performs a specific task. Functions allow you to break down your code into smaller, more manageable pieces, making it easier to understand, maintain, and reuse.
message = “Hello, ” + name + “! How are you doing?”
Call the function
greeting = greet(“Alice”)
Q22.How do you call a function with arguments in Python?
message = “Hello, ” + name + “! How are you doing?”
# Call the function with different arguments
greeting1 = greet(“Alice”)
greeting2 = greet(“Bob”)
In this example, we call the greet function twice with different arguments (“Alice” and “Bob”). Each time the function is called, it receives the respective name as an argument and returns a customized greeting message. The returned messages are stored in the variables greeting1 and greeting2, and we print them to the console.
Q23.What is a lambda function, and how is it different from a regular function?
Ans.A lambda function in Python is a small anonymous function that can have any number of arguments but can only have one expression.
It is defined using the lambda keyword and is often used when you need a simple function for a short period or when you want to pass a function as an argument to another function.Ex:-
add = lambda x, y: x + y
result = add(3, 5)
print(result) # Output: 8
In this example, we define a lambda function add that takes two arguments x and y, and returns their sum x + y. We then call this lambda function with x = 3 and y = 5, and the result (8) is stored in the result variable and printed.
Q24.Explain the concept of a “docstring” in Python.
Ans.In Python, a “docstring” (short for “documentation string”) is a special type of string used to document modules, classes, functions, or methods in a human-readable format.
Docstrings are used to provide useful information about the purpose, behavior, and usage of the code elements they document.
They serve as documentation for developers who read and use the code, helping them understand how to use the code correctly and what it does without having to read the implementation details.
Q25.How do you import modules in Python?
Ans.1. Import the Entire Module:
To import an entire module, you can use the import keyword followed by the module name.Ex:-
result = math.sqrt(25)
print(result) # Output: 5.0
In this example, we import the math module and use the math.sqrt() function to calculate the square root of 25.
Q26.What is a virtual environment, and why would you use it?
Ans.A virtual environment in Python is a self-contained directory that contains a specific Python interpreter and its own set of installed packages.
It allows you to create isolated and independent environments for your Python projects, ensuring that each project has its own dependencies and doesn’t interfere with other projects or the system-wide Python installation.
Q27.How can you install external packages in Python?
Ans.Installing Packages with pip:
To install an external package using pip, open a terminal or command prompt, and use the following syntax:
pip install package_name
Q28.Explain the difference between local and global variables.
Ans.The difference between local and global variables are:-
|Local Variables||Global Variables|
|Local variables are declared inside a function and are only accessible within that specific function.||Global variables are declared outside any function, at the top-level of the code, and have a global scope.|
|They have a local scope, meaning they exist and can be accessed only within the block of code where they are defined.||They are accessible throughout the entire program, including inside functions.|
|Local variables are created when the function is called and are destroyed when the function completes its execution or returns a value.||Global variables are created when the program starts execution and persist until the program terminates.|
Q29.What is a Python decorator, and how can you use it?
Ans.In Python, a decorator is a powerful and flexible concept used to modify or extend the behavior of functions or methods without changing their actual code.
Decorators allow you to wrap a function with another function, effectively adding functionality before, after, or around the original function’s execution.Using a Decorator:
To use a decorator, you apply it to a function using the @decorator_function syntax (the “@” symbol followed by the decorator’s name). This tells Python to treat the function as decorated by the specified decorator.
Q30.What is a list in Python?
Ans.In Python, a list is a mutable, ordered collection of items. It contain elements of different data types, such as integers, strings, floats, or even other lists.
Lists are one of the most versatile data structures in Python and are commonly used for storing and manipulating sequences of items.
Q31.How do you create a tuple, and what are its characteristics?
Ans.In Python, a tuple is an ordered, immutable collection of elements.
Tuples are defined using parentheses () and can contain elements of different data types, similar to lists. The main characteristics of tuples are:
1.Tuples are immutable, which means once created, their elements cannot be changed, added, or removed
2.You can find the length of a tuple using the len() function and perform slicing to extract a sublist (slice) from a tuple, just like with lists.
3.You can concatenate two tuples using the + operator, which creates a new tuple containing all the elements of both tuples.
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