On Sun, 12 Sep 2010 09:03:49 am Walter Prins wrote:
> So, perhaps it's an idea to call dir() on a given object and see
> whether the object provides the necessary methods to function, e.g.
> __iter__, __delitem__, __setitem__ and friends?
There's no need to do this:
attributes = dir(obj)
if '__iter__' in attributes and '__len__' in attributes:
print "Quacks like a list"
else:
print "Not like a list"
when you can do this:
if hasattr(obj, '__iter__') and hasattr(obj, '__len__'):
print "Quacks like a list"
else:
print "Not like a list"
or this:
try:
obj.__iter__
obj.__len__
except AttributeError:
print "Not like a list"
else:
print "Quacks like a list"
or even
try:
iter(obj)
len(obj)
except TypeError:
print "Not like a list"
else:
print "Quacks like a list"
Where possible, the last version is to be preferred, because it doesn't
care about internal details which might change.
--
Steven D'Aprano
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