12.4: Variable-length argument tuples
- Page ID
- 40797
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Functions can take a variable number of arguments. A parameter name that begins with * gathers arguments into a tuple. For example, printall takes any number of arguments and prints them:
def printall(*args):
print(args)
The gather parameter can have any name you like, but args is conventional. Here’s how the function works:
>>> printall(1, 2.0, '3') (1, 2.0, '3')
The complement of gather is scatter. If you have a sequence of values and you want to pass it to a function as multiple arguments, you can use the * operator. For example, divmod takes exactly two arguments; it doesn’t work with a tuple:
>>> t = (7, 3) >>> divmod(t) TypeError: divmod expected 2 arguments, got 1
But if you scatter the tuple, it works:
>>> divmod(*t) (2, 1)
Many of the built-in functions use variable-length argument tuples. For example, max and min can take any number of arguments:
>>> max(1, 2, 3) 3
But sum does not.
>>> sum(1, 2, 3) TypeError: sum expected at most 2 arguments, got 3
As an exercise, write a function called sum_all that takes any number of arguments and returns their sum.