3.4: Variable-Length Argument Tuples
- Page ID
- 15428
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)
Exercise \(\PageIndex{1}\)
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
Write a function called sumall
that takes any number of arguments and returns their sum.