How to test if object is sequence, or iterable?
Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) Regards, --Tim -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Tim N. van der Leeuw a écrit : Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) isiterable = lambda obj: isinstance(obj, basestring) \ or getattr(obj, '__iter__', False) Should cover most cases. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Bruno Desthuilliers wrote: Tim N. van der Leeuw a écrit : Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) isiterable = lambda obj: isinstance(obj, basestring) \ or getattr(obj, '__iter__', False) Should cover most cases. Yes, that seems to cover all cases I can think of, indeed. Funny though, that string objects do not have an '__iter__' method, but are still iterable... But it will make most of my use-cases easier: Often I want to iterate over something, if it's an iterable, except when it's a string. Thanks, --Tim -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Tim N. van der Leeuw [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). How about try: it = iter(possible_iterable) except TypeError: bail() Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
In [EMAIL PROTECTED], Bruno Desthuilliers wrote: Tim N. van der Leeuw a écrit : Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) isiterable = lambda obj: isinstance(obj, basestring) \ or getattr(obj, '__iter__', False) Should cover most cases. What about objects that just implement an apropriate `__getitem__()` method? Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Marc 'BlackJack' Rintsch a écrit : In [EMAIL PROTECTED], Bruno Desthuilliers wrote: Tim N. van der Leeuw a écrit : Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) isiterable = lambda obj: isinstance(obj, basestring) \ or getattr(obj, '__iter__', False) Should cover most cases. What about objects that just implement an apropriate `__getitem__()` method? Hmmm... (quick test) Good point. FWIW, Terry's solution might be far better. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Tim, An object is iterable if it implements the iterator protocol. A good enough check to see if it does is to check for the presense of the __iter__() method. The way to do it is: hasattr(object,'__iter__') You are correct in the fact that you check if an object is iterable rather than using isinstance to check if it is of a partucular type. You are doing things 'the pythonic way' ;) Nick Vatamaniuc Tim N. van der Leeuw wrote: Hi, I'd like to know if there's a way to check if an object is a sequence, or an iterable. Something like issequence() or isiterable(). Does something like that exist? (Something which, in case of iterable, doesn't consume the first element of the iterable) Regards, --Tim -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test if object is sequence, or iterable?
Nick Vatamaniuc [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
Tim,
An object is iterable if it implements the iterator protocol
There are presently two iterator protocols. The old one will be likely be
dropped in 3.0 (currently being discussed).
. A good
enough check to see if it does is to check for the presense of the
__iter__() method. The way to do it is:
hasattr(object,'__iter__')
Sorry, this check for the newer and nicer protocol but not the older one.
hasattr('abc', '__iter__')
False
This may change in 2.6. The defacto *version-independent* way to determine
iterability is to call iter(ob). If it returns an iterator, you can
iterate; if it raises TypeError, you cannot. Any it should be patched as
necessary by the developers to continue doing the right thing in future
versions.
Terry Jan Reedy
--
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