Python Programming Function Arguments Default Keyword Variable Length Complete Guide

Python Programming Function Arguments: Default, Keyword, Variable Length

Default Arguments

Default arguments allow functions to be called with fewer arguments than defined. If an argument is not provided when the function is called, the default value is used. This feature enhances the flexibility of functions by providing sensible defaults that can be overridden as necessary.

Syntax:

def function_name(arg1, arg2=default_value):
    # Function body

Example:

def greet(name, greeting="Hello"):
    print(f"{greeting}, {name}!")

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

Key Points:

• Default arguments must be placed at the end of the function definition.
• They provide a fallback value if the calling code doesn’t supply one.

Keyword Arguments

Keyword arguments improve code readability by explicitly linking argument names with their values. You can specify arguments in any order as long as each keyword is associated with its value.

Syntax:

function_name(arg1=value1, arg2=value2)

Example:

def display_info(name, age, city):
    print(f"Name: {name}, Age: {age}, City: {city}")

display_info(name="Alice", age=30, city="New York")
display_info(city="London", name="Bob", age=25)

Key Points:

• Makes the function call clearer and less error-prone, especially when dealing with functions that have many parameters.
• Arguments can be passed in any order, which increases flexibility.

Variable Length Arguments

Variable length arguments allow functions to accept any number of arguments. Python supports two types: *args for positional arguments and **kwargs for keyword arguments.

• *args: Captures a variable number of positional arguments. It appears as a tuple within the function.
• **kwargs: Captures a variable number of keyword arguments. It appears as a dictionary within the function.

Syntax:

def function_name(*args, **kwargs):
    # Function body

Example:

def print_numbers(*args):
    for num in args:
        print(num)

print_numbers(1, 2, 3, 4)

def print_details(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

print_details(name="Charlie", age=28, city="Los Angeles")

Output:

1
2
3
4
name: Charlie
age: 28
city: Los Angeles

Key Points:

• *args is useful when you don’t know in advance how many arguments will be passed.
• **kwargs allows passing variable-length keyword arguments, making functions more versatile and user-friendly.

Combining Argument Types

You can combine these types of arguments to create more flexible and reusable functions, but keep in mind the order:

1. Mandatory positional arguments
2. Default positional arguments
3. *args
4. Default keyword arguments
5. **kwargs

Example:

def complex_function(required, optional="default", *args, **kwargs):
    print(f"Required argument: {required}")
    print(f"Optional argument: {optional}")
    print("Variable positional arguments:")
    for arg in args:
        print(arg)
    print("Variable keyword arguments:")
    for key, value in kwargs.items():
        print(f"{key}: {value}")

complex_function("Mandatory", "Special", 100, 200, name="Dave", role="Engineer")

Output: