Defining and Calling Functions

Defining a Function

A function is a block of code that performs a specific task. In Python, you define a function using the def keyword followed by the function name, parentheses, and a colon. The code block that defines the function is indented below the colon.

Syntax:

Python

def function_name(parameters):
  """Docstring: Explains what the function does"""
  # Function body
  return value  # Optional

• def: Keyword to indicate the start of a function definition.
• function_name: The name you give to the function.
• parameters: Optional variables that can receive values when the function is called.
• docstring: An optional string that explains what the function does.
• return: Optionally returns a value from the function.

Example:

Python

def greet(name):
  """Greets a person by name."""
  print("Hello,", name, "!")

Calling a Function

To execute a function, you call it by its name followed by parentheses. If the function requires parameters, you pass the values within the parentheses.  

Syntax:

Python

function_name(arguments)

• function_name: The name of the function you want to call.
• arguments: Values passed to the function, corresponding to the parameters.

Example:

Python

greet("Alice")  # Output: Hello, Alice!

Parameters and Arguments

• Parameters are the variables defined in the function’s definition. They act as placeholders for values that will be passed when the function is called.
• Arguments are the actual values passed to the function when it’s called. They are assigned to the corresponding parameters.

Example:

Python

def add(x, y):
  """Adds two numbers."""
  result = x + y
  return result

sum = add(3, 5)  # Here, 3 and 5 are arguments
print(sum)  # Output: 8

Return Statement

The return statement specifies the value that a function sends back to the caller. If no return statement is present, the function implicitly returns None.

Example:

Python

def multiply(x, y):
  """Multiplies two numbers."""
  return x * y

product = multiply(4, 2)
print(product)  # Output: 8

Key Points

• Functions help organize code and make it reusable.
• Parameters provide flexibility in function behavior.
• The return statement is used to send values back from a function.
• Function names should be descriptive and follow naming conventions.

By understanding these concepts, you can effectively define and use functions in your Python programs.

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