How does the asterisk (*) work in Python function definitions?

Understanding the Asterisk (*) in Python Function Definitions

In Python, the asterisk (*) holds significant meaning in defining functions. The reference documentation for function definitions sheds light on its usage:

• Excess Positional Arguments: The syntax form *identifier accepts any remaining positional parameters not included in the function's signature and initializes them to a tuple. By default, an empty tuple is assigned if there are no excess positional arguments.
• Excess Keyword Arguments: The syntax form **identifier stores any additional keyword arguments not accounted for in the function's signature and assigns them to a new dictionary. The default is an empty dictionary if there are no excess keyword arguments.

Here are tangible examples to illustrate their application:

Example 1: Excess Keyword Arguments

def foo(a, b, c, **args):
    print(f"a = {a}")
    print(f"b = {b}")
    print(f"c = {c}")
    print(args)

foo(a="testa", d="excess", c="testc", b="testb", k="another_excess")

Example 2: Excess Positional Arguments

def foo(a, b, c, *args):
    print(f"a = {a}")
    print(f"b = {b}")
    print(f"c = {c}")
    print(args)

foo("testa", "testb", "testc", "excess", "another_excess")

Unpacking Arguments

The asterisk can also be used to unpack dictionaries or tuples into function arguments:

Example 3: Unpacking a Dictionary

def foo(a, b, c, **args):
    print(f"a={a}")
    print(f"b={b}")
    print(f"c={c}")
    print(f"args={args}")

argdict = {"a": "testa", "b": "testb", "c": "testc", "excessarg": "string"}
foo(**argdict)

Example 4: Unpacking a Tuple

def foo(a, b, c, *args):
    print(f"a={a}")
    print(f"b={b}")
    print(f"c={c}")
    print(f"args={args}")

argtuple = ("testa", "testb", "testc", "excess")
foo(*argtuple)

By understanding the asterisk's usage in Python function definitions, you can effectively handle excess arguments and unpack data into function arguments.

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