In Python, how do I determine if an object is iterable?

Question

Is there a method like isiterable? The only solution I have found so far is to call

hasattr(myObj, \'__iter__\')

But I am not

Answer 1

The easiest way, respecting the Python's duck typing, is to catch the error (Python knows perfectly what does it expect from an object to become an iterator):

class A(object):
    def __getitem__(self, item):
        return something

class B(object):
    def __iter__(self):
        # Return a compliant iterator. Just an example
        return iter([])

class C(object):
    def __iter__(self):
        # Return crap
        return 1

class D(object): pass

def iterable(obj):
    try:
        iter(obj)
        return True
    except:
        return False

assert iterable(A())
assert iterable(B())
assert iterable(C())
assert not iterable(D())

Notes:

1. It is irrelevant the distinction whether the object is not iterable, or a buggy __iter__ has been implemented, if the exception type is the same: anyway you will not be able to iterate the object.

2. I think I understand your concern: How does callable exists as a check if I could also rely on duck typing to raise an AttributeError if __call__ is not defined for my object, but that's not the case for iterable checking?

   I don't know the answer, but you can either implement the function I (and other users) gave, or just catch the exception in your code (your implementation in that part will be like the function I wrote - just ensure you isolate the iterator creation from the rest of the code so you can capture the exception and distinguish it from another TypeError.