Python def

In Python, the def keyword is used to define a function. Functions allow users to group related code into blocks that can be executed repeatedly without rewriting the same lines. Using functions helps improve modularity, reduce redundancy, and increase readability.

Syntax

def function_name(parameters):
  """
  Optional docstring
  """
  # Function body
  return result

In the syntax:

• function_name: The name of the function.
• parameters (Optional): The inputs that the function can accept.
• return (Optional): The value that the function returns.

Example 1: A Simple Greeting Function

In this example, the function greet() prints the given greeting when called:

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

greet()

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Here is the output:

Hello, Codecademy!

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Example 2: Function with Parameters

In this example, the add() function takes two parameters and returns their sum:

def add(a, b):
  return a + b

result = add(5, 3)

print("Sum:", result)

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Here is the output:

Sum: 8

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Codebyte Example: Function with Default Parameter

In this example, the power() function uses a default parameter value (2) for the exponent parameter. If an argument is not provided for this parameter, the default value will be taken:

def power(base, exponent=2):
  return base ** exponent

print(power(4))
print(power(3, 3))

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Here is the output:

16
27

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Frequently Asked Questions

1. Can a function return multiple values?

Yes. Python functions have the ability to return multiple values as a tuple:

def get_coordinates():
  return 10, 20

x, y = get_coordinates()

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2. Can you define a function inside another function?

Yes. Python supports nested functions:

def outer():
  def inner():
    print("Inner function")
  inner()

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3. What happens if you call a function before it’s defined?

Python will raise a NameError. Functions must be defined before they are called in the code flow.