Python User defined functions

Python User defined functions

In Python, a user-defined function is a block of related statements designed to perform a specific task. Functions help break down our programs into smaller and modular chunks, making them organized and manageable.

Here's a basic outline of how to create and use user-defined functions in Python:

1. Defining a Function:

Use the def keyword to declare a function:

def function_name(parameters): """docstring (optional)""" # function body statements
  • function_name: The name of the function. It should be descriptive and follow the same naming conventions as variables.
  • parameters (or arguments): The values you pass into the function. They are optional.
  • docstring: An optional description of what the function does. You can access it with the help() function or the .__doc__ attribute.
  • statements: The main code that the function will execute when called.

2. Calling a Function:

After defining a function, you can call it by its name:

function_name(arguments)

3. Example:

Let's look at a simple function that adds two numbers:

def add_numbers(a, b): """This function returns the sum of two numbers.""" return a + b # Call the function result = add_numbers(5, 3) print(result) # Outputs: 8

4. Return Values:

Functions can return results using the return statement. Once the return statement is executed, the function's execution stops, and the value is returned to the caller:

def multiply_numbers(a, b): return a * b

5. Default Argument Values:

You can provide default values for arguments:

def greet(name, msg="Hello"): return f"{msg}, {name}!" print(greet("Alice")) # Outputs: Hello, Alice! print(greet("Bob", "Hi")) # Outputs: Hi, Bob!

6. Variable-length Arguments:

You can pass a variable number of arguments using the *args (for non-keyword arguments) and **kwargs (for keyword arguments) conventions:

def print_args(*args): for arg in args: print(arg) print_args(1, 2, 3, 4) # Outputs: 1, 2, 3, 4 on separate lines def print_kwargs(**kwargs): for key, value in kwargs.items(): print(f"{key} = {value}") print_kwargs(a=1, b=2, c=3) # Outputs: a = 1, b = 2, c = 3 on separate lines

User-defined functions are a fundamental concept in programming and a crucial tool for promoting code reuse, modularity, and clarity.

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