Python function with example

What are Python Functions and How to use functions in python?

A Python function is a reusable block of code that performs a specific task.

Instead of writing the same code multiple times, you can create a function of that code and call it whenever needed, which helps reduce code length and makes it easier to read and maintain.

Syntax for Defining a Function:

def function_name():
    # block of code that is use again and again

How to create and call a function?

Declaration of function:

To declare (or define) a function in Python, you use the def keyword, followed by the function name, parentheses, and a colon. The code inside the function is indented.

def heyFun():
    # Your code

 Calling a function:

To call a function, you use the function name followed by parentheses.

You can call the function the number of times you need the code written inside the function.

heyFun()
heyFun()
heyFun()

For Example:

When we are not use the function:

a very basic example..Let's suppose this code is repeated again and again:

print("this is a python function.")
print("you learn from the eagle eye tutorials.")

print("this is a python function.")
print("you learn from the eagle eye tutorials.")

print("this is a python function.")
print("you learn from the eagle eye tutorials.")

Output:

this is a python function.
you learn from the eagle eye tutorials.
this is a python function.
you learn from the eagle eye tutorials.
this is a python function.
you learn from the eagle eye tutorials.

Optimize this code with function:

def printstatments():
    print("this is a python function.")
    print("you learn from the eagle eye tutorials.")

printstatments()
printstatments()

Now you can simply call this function when you need its inner code.

Output:

this is a python function.
you learn from the eagle eye tutorials.
this is a python function.
you learn from the eagle eye tutorials.

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What is return Statement in Python?

The return statement in Python is used to send a value back from a function to the place where the function was called. If there is no return statement, the function will return None by default.

Syntax:

def function_name():
    # code to execute
    return value  # returns 'value' to where the function was called

Example:

def printData():
    a = "how are you"
    return a

x = printData()

print(x)

Output:

how are you

Explanation:

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Interview-style questions related to Python functions with answers and examples

Question 1. What is a function in Python?

Answer: A function in Python is a reusable block of code designed to perform a specific task. Functions help organize code, making it more readable and efficient.

Example:

def say_hello():
    print("Hello, World!")

say_hello()

Answer:

Hello, World!

 

 Question 2. How do you declare a function in Python?

Answer: You declare a function in Python using the def keyword, followed by the function name, parentheses, and a colon. The code inside the function is indented.

Example:

def say_hello():
    print("Hello, everyone!")

# This function is now declared and can be called.

 

 Question 3. How do you call a function in Python?

Answer: You call a function by writing its name followed by parentheses. This tells Python to execute the code inside the function.

Example:

def greet():
    print("Good morning!")

greet() 

Answer:

Good morning!

 

 Question 4. Why do we use functions in Python?

Answer: Functions are used to make code reusable, reduce repetition, and improve organization. This helps keep code clean, efficient, and easy to maintain.

Example:

# Without function
print("Hello, Alice!")
print("Hello, Bob!")

# With function
def greet():
    print("Hello!")

greet()
greet()

Output:

Hello, Alice!
Hello, Bob!
Hello!
Hello!

 

 Question 5. Can you create a function with no code in it?

Answer: Yes, you can create a function with no code using the pass statement as a placeholder. This is useful if you plan to implement the function later.

Example:

def placeholder():
    pass

placeholder()

 

 Question 6. What happens if you call a function without defining it?

Answer: If you call a function that hasn't been defined, Python will throw a NameError, indicating that the function is not recognized.

Example:

greet()  # Error: NameError: name 'greet' is not defined

def greet():
    print("Hello!")

Output:

NameError: name 'greet' is not defined

 

  Question 7. Can a function be called multiple times?

Answer: Yes, a function can be called as many times as needed. This allows you to reuse code without duplicating it.

Example:

def greet():
    print("Hi there!")

greet()  
greet()  

Output:

Hi there!
Hi there!

 

  Question 8. What does it mean to “declare” a function?

Answer: Declaring a function means creating it with the def keyword, giving it a name, and writing the code it will execute. Declaring does not run the function; it just defines it.

Example:

def say_hello():
    print("Hello, World!")

# The function `say_hello` is now declared but has not been run yet.

 

  Question 9. What is the difference between declaring and calling a function?

Answer: Declaring a function means defining it, so Python knows what the function will do. Calling a function means executing the code inside it by writing the function name followed by parentheses.

Example:

# Declaring the function
def greet():
    print("Hello, Python!")

# Calling the function
greet()  

Output:

Hello, Python!

 

  Question 10. How does using functions make debugging easier?

Answer: Functions allow you to separate code into smaller, manageable sections. This makes it easier to find and fix errors, as you can test each function individually.

Example:

def greet():
    print("Hello!")

def farewell():
    print("Goodbye!")

# If there's an issue, you can check `greet()` and `farewell()` separately.
greet()     
farewell()  

Output:

Hello!
Goodbye!