Python Function

A function is a block of organized, reusable code that is used to perform a single, related action. Functions provide better modularity for your application and a high degree of code reusing.

Defining a Function

You can define a function using the def keyword, followed by the function name and a set of parentheses (). Optionally, you can add parameters inside the parentheses. The block of code within every function starts with a colon : and is indented.

For example, the following function takes a string as parameter and prints it to the console:

def greet(name):
  print("Hello, " + name)

Calling a Function

To call a function, you simply use the function name followed by a set of parentheses () and pass any required parameters. For example:

greet("John")

This will print “Hello, John” to the console.

Returning a Value

By default, functions return None. However, you can use the return statement to return a value from the function. For example:

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

result = get_sum(1, 2)
print(result)  # 3

Optional Parameters

You can define default values for function parameters, which makes them optional. If a default value is provided for a parameter, the corresponding argument can be omitted from the function call. For example:

def greet(name, greeting="Hello"):
  print(greeting + ", " + name)

greet("John")       # Hello, John
greet("John", "Hi") # Hi, John

Variable-Length Arguments

Sometimes, you may need to define a function that can accept a variable number of arguments. In Python, this is done using the *args and **kwargs syntax.

*args is used to pass a non-keyworded, variable-length argument list to the function. **kwargs is used to pass a keyworded, variable-length argument list to the function. For example:

def print_info(name, *args, **kwargs):
  print("Name:", name)
  print("Arguments:", args)
  print("Keyword arguments:", kwargs)

print_info("John", 1, 2, 3, job="developer", age=30)

This will print the following output:

Name: John
Arguments: (1, 2, 3)
Keyword arguments: {'job': 'developer', 'age': 30}