In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] wrote:
>I want to be able to pass a sequence (tuple, or list) of objects to a
>function, or only one.
>
>It's easy enough to do:
>
>isinstance(var, (tuple, list))
>
>But I would also like to accept generators. How can I do this?
>
>Anything else is assumed to be a single value (my fault if I pass a
>dict or something else to the function) and I make it into a tuple with
>a single value (var, ) in order to simplify the algorithm (wasn't there
>a special name for a one item tuple? Its been a while since I've
>programmed in Python.)
>
>Is there an easy way to do that?
Here is the code I use for that purpose, but it does not handle
generators or iterators. You could easily combine this with code
suggested in other replies to accomplish that. (I intentionally excluded
iterators because I didn't need them and they can be unbounded. Still,
now that they are so widely used it may be worth reconsidering.)
def isSequence(item):
"""Return True if the input is a non-string sequential collection,
False otherwise. Note: dicts and sets are not sequential.
"""
try:
item[0:0]
except (AttributeError, TypeError):
return False
return not isString(item)
def isString(item):
"""Return True if the input is a string-like sequence.
Strings include str, unicode and UserString objects.
From Python Cookbook, 2nd ed.
"""
return isinstance(item, (basestring, UserString.UserString))
def asSequence(item):
"""Converts one or more items to a sequence,
If item is already a non-string-like sequence, returns it unchanged,
else returns [item].
"""
if isSequence(item):
return item
else:
return [item]
I then use asSequence on each argument that can either be one item or a
sequence of items (so I can always work on a sequence).
-- Russell
P.S. this code is from RO.SeqUtil
<http://www.astro.washington.edu/rowen/ROPython.html>
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