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

What is the Significance of the Asterisk (*) in Python Function Definitions?

In Python, the asterisk (*) operator plays a pivotal role in defining functions.

Function Definitions

When used in function definitions, the asterisk has two forms:

• *identifier signifies a tuple that accumulates any excess positional arguments not explicitly defined in the function signature.
• **identifier represents a dictionary that aggregates any excess keyword arguments.

Examples

Consider the following function definition:

def get(self, *a, **kw)

• The asterisk () after the parameter a* collects any remaining positional arguments into a tuple.
• The double asterisk (*) after the parameter kw* gathers any remaining keyword arguments into a dictionary.

Function Calls

When calling a function with excess arguments, they can be passed using the asterisk syntax:

Positional Arguments

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

In this example, the excess positional arguments ("excess" and "another_excess") are packed into a tuple.

Keyword Arguments

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

The excess keyword arguments ("d" and "k") are collected into a dictionary.

Unpacking Arguments

You can also unpack dictionaries or tuples into function arguments using the asterisk syntax:

Unpacking a Dictionary

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

Unpacking a Tuple

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

Conclusion

The asterisk (*) operator provides a convenient way to handle excess arguments in Python function definitions and calls, enabling flexibility and code readability.

The above is the detailed content of How does the asterisk (*) operator work in Python function definitions and calls?. For more information, please follow other related articles on the PHP Chinese website!