Multiple Function Parameters

A function can have more than one parameter. Parameters are listed in the def line separated by commas.

Example: Addition

This function takes two numbers and prints a sentence describing their sum:

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>>> def print_sum(a, b):
...     total = a + b
...     print(f"The sum of {a} and {b} is {total}.")
...
>>> print_sum(3, 4)
The sum of 3 and 4 is 7.
>>> print_sum(10, 25)
The sum of 10 and 25 is 35.

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When you call print_sum(3, 4): - parameter a receives the value 3 - parameter b receives the value 4

This matching is positional — the first argument goes to the first parameter, the second to the second, and so on.

Keyword Arguments

You can also pass arguments by name (called keyword arguments):

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>>> def print_sum(a, b):
...     total = a + b
...     print(f"The sum of {a} and {b} is {total}.")
...
>>> print_sum(b=4, a=3)
The sum of 3 and 4 is 7.

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With keyword arguments, order does not matter. We will see keyword arguments used more heavily later (for example, print(end="") uses them).

Default Values

Parameters can have default values. If the caller omits the argument, the default is used:

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>>> def greet(name, greeting="Hello"):
...     print(f"{greeting}, {name}!")
...
>>> greet("Alice")            # uses default greeting
Hello, Alice!
>>> greet("Bob", "Hi there")  # overrides default
Hi there, Bob!

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Parameters with default values must come after parameters without defaults.