Passing a tuple to a function as multiple arguments

Gabriel Genellina gagsl-py2 at yahoo.com.ar
Fri Sep 7 05:35:24 CEST 2007


En Fri, 07 Sep 2007 00:02:12 -0300, Ben Warren <bwarren at qstreams.com>  
escribi�:

> Hello,
>
> Let's say I have a function with a variable number of arguments (please  
> ignore syntax errors):
>
> def myfunc(a,b,c,d,...):
>
> and I have a tuple whose contents I want to pass to the function.  The  
> number of elements in the tuple will not always be the same.
>
> T = A,B,C,D,...
>
> Is there a way that I can pass the contents of the tuple to the function  
> without explicitly indexing the elements?  Something like:
>
> myfunc(magic(T))

Use *T when calling the function:

py> def myfunc(a, b, c, d=None, e=None):
...   print a,b,c,d,e
...
py> T = 1,2,3,4,5
py> myfunc(*T)
1 2 3 4 5
py> T = 1,2,3
py> myfunc(*T)
1 2 3 None None
py> T = 1,2
py> myfunc(*T)
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
TypeError: myfunc() takes at least 3 arguments (2 given)

A similar syntax works when defining a function: *args will receive all  
remaining positional arguments joined into a tuple:

py> def otherfunc(a, b, *args):
...   print a, b, args
...
py> otherfunc(1,2,3,4,5)
1 2 (3, 4, 5)
py> T = 1,2,3,4
py> otherfunc(*T)
1 2 (3, 4)
py> otherfunc('a','b','c',*T)
a b ('c', 1, 2, 3, 4)

This is covered in the Python Tutorial at  
<http://docs.python.org/tut/node6.html#SECTION006700000000000000000> and  
you can read the nasty details here <http://docs.python.org/ref/calls.html>

-- 
Gabriel Genellina




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