How Do `*args` and `kwargs` Handle Variable Arguments in Python Functions?

Understanding the Significance of (Star/Asterisk) and * (Double Star/Asterisk) in Parameters

In Python function definitions, the and * operators provide powerful idioms for handling arbitrary numbers of arguments.

Positional Arguments: *args

• The *args parameter allows a function to accept a variable number of positional arguments.
• These arguments are collected into a tuple that can be accessed within the function.

Example:

def foo(x, y, *args):
    pass

foo(1, 2, 3)
# args = (3,)

Keyword Arguments: kwargs**

• The **kwargs parameter allows a function to accept any number of keyword arguments.
• These arguments are collected into a dictionary where the keys are the argument names and the values are the argument values.

Example:

def bar(x, y, **kwargs):
    pass

bar(x=1, y=2, name='John', age=27)
# kwargs = {'name': 'John', 'age': 27}

Mixing Fixed and Variable Arguments

• Both args and *kwargs can be combined with normal fixed arguments to provide flexibility in function definitions.

Example:

def foo(kind, *args, bar=None, **kwargs):
    print(kind, args, bar, kwargs)

foo(123, 'a', 'b', apple='red')
# 123 ('a', 'b') None {'apple': 'red'}

Additional Uses

• • can be used to unpack argument lists when calling a function.
• In Python 3, and * can be used on the left side of an assignment to unpack iterables into variables.
• Python 3.6 introduces a new syntax that restricts positional arguments after *.

Note:

• Python uses dictionaries to represent keyword arguments, which maintain insertion order in Python 3.6 .
• kwargs dictionaries maintain insertion order in Python 3.7 and above, even for non-CPython implementations.

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