determining the number of output arguments

Jeff Shannon jeff at ccvcorp.com
Mon Nov 15 22:32:29 CET 2004


Darren Dale wrote:

>Hello,
>
>def test(data):
>
>	i = ? This is the line I have trouble with
>
>	if i==1: return data 
>	else: return data[:i]
>
>a,b,c,d = test([1,2,3,4])
>
>How can I set i based on the number of output arguments defined in 
>(a,b,c,d)?
>  
>

Something like this:

def test(*args, **kwargs):
    i = len(args) + len(kwargs)

should work.  But note that the usage example you gave will result in i 
having a value of 1 -- you're passing in a single argument (which is a 
list).

Of course, if you're always going to be passing a sequence into your 
function, and you want to get the length of that sequence, then it's 
pretty simple:

def test(data):
    i = len(data)
    return data[:i]

Note, however, that this function is effectively a no-op as it stands.  
Presumably you're intending to do something to transform data, which may 
change its length?  Otherwise, it would be simpler to just modify the 
list (or a copy of it) in-place in a for loop / list comp, and not worry 
about the length at all.

Jeff Shannon
Technician/Programmer
Credit International





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