How Do Single and Double Asterisks (*) Unpack Arguments in Python Functions?

Unpacking Arguments in Python with and (Double Star/Asterisk)*

In Python, the and * operators play crucial roles in unpacking arguments when calling functions.

Single Star *:
The single star (*) unpacks a sequence or collection into positional arguments. For example, consider the function:

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

The code below uses * to unpack the tuple values:

values = (1, 2)
s = add(*values)

This is equivalent to writing:

s = add(1, 2)

Double Star **:
The double star (**) performs a similar operation for dictionaries, providing values for named arguments. Consider the function:

def sum(a, b, c, d):
    return a + b + c + d

Unpacking the dictionary values2 using ** yields the following:

values2 = { 'c': 10, 'd': 15 }
s = add(**values2)

This is equivalent to:

s = sum(a=1, b=2, c=10, d=15)

Combination of and :*
Both and * can be used simultaneously in the same function call. For instance:

values1 = (1, 2)
values2 = { 'c': 10, 'd': 15 }
s = add(*values1, **values2)

This is equivalent to:

s = sum(1, 2, c=10, d=15)

Parameter Unpacking:
In addition to unpacking arguments, and * can also be used for parameter unpacking in function definitions.

• A parameter marked with * receives any number of positional arguments as a tuple.
• A parameter marked with ** receives all keyword arguments as a dictionary.

For example:

def add(*values):
    # ...

def get_a(**values):
    # ...

Performance Implications:
The performance implications of using and * are generally minimal. The unpacking operation involves minimal overhead and does not affect the efficiency of the function itself. However, excessive unpacking can make code less readable and maintainable.

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