how to tell a variable is iterable but not a string

Question

I have a function that take an argument which can be either a single item or a double item:

def iterable(arg)
    if #arg is an iterable:
        print \"yes         


        

Answer 1

I realise this is an old post but thought it was worth adding my approach for Internet posterity. The function below seems to work for me under most circumstances with both Python 2 and 3:

def is_collection(obj):
    """ Returns true for any iterable which is not a string or byte sequence.
    """
    try:
        if isinstance(obj, unicode):
            return False
    except NameError:
        pass
    if isinstance(obj, bytes):
        return False
    try:
        iter(obj)
    except TypeError:
        return False
    try:
        hasattr(None, obj)
    except TypeError:
        return True
    return False

This checks for a non-string iterable by (mis)using the built-in hasattr which will raise a TypeError when its second argument is not a string or unicode string.