4.11 Arbitrary Argument Lists

  • Functions with arbitrary argument lists, such as built-in functions min and max, can receive any number of arguments.
  • Function min's documentation states that min has two required parameters (named arg1 and arg2) and an optional third parameter of the form *args, indicating that the function can receive any number of additional arguments.
  • The * before the parameter name tells Python to pack any remaining arguments into a tuple that’s passed to the args parameter.

Defining a Function with an Arbitrary Argument List

  • average function that can receive any number of arguments.
In [1]:
def average(*args):
    return sum(args) / len(args)
  • The *args parameter must be the rightmost parameter.
In [2]:
average(5, 10)
Out[2]:
7.5
In [3]:
average(5, 10, 15)
Out[3]:
10.0
In [4]:
average(5, 10, 15, 20)
Out[4]:
12.5

Passing an Iterable’s Individual Elements as Function Arguments

  • Can unpack a tuple’s, list’s or other iterable’s elements to pass them as individual function arguments.
  • The * operator, when applied to an iterable argument in a function call, unpacks its elements.
In [5]:
grades = [88, 75, 96, 55, 83]
In [6]:
average(*grades)
Out[6]:
79.4
  • Equivalent to average(88, 75, 96, 55, 83).

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