How can I verify that a passed argument is an interible collection?

[Larry Bates]

Others may know better ways but the 2 I know of are:

1) If you know that the arguments will be lists or tuples
you can use isinstance().

if not isinsance(arg, (list, tuple):
    print "arg must be list or tuple)

2) Or if you not you could see if the argument has next and
__iter__ methods (more general solution)

if  hasattr(arg, 'next') and not hasattr(arg, '__iter__'):
    # perform work on iterable

else:
    print "arg must be an iterable"


Larry Bates


Charles Krug wrote:
> List:
> 
> I'm working on some methods that operate on (mathematical) vectors as
> in:
> 
> def Convolution(x, y)
> """Returns a list containing the convolution of vectors x and y"""
> 
> Is there any way to determine at runtime that x and y are iterible
> collections?
> 
> Do I *coughs* simply *coughs* trap the exception created by:
> 
>     for v in x:
> 
> when v is a scaler quantity?
> 
> Thanks
> 
> 
> Charles
>