def is_in(obj, l):
    """判断obj对象是否在l中，判断相等的逻辑是is，而不是=
    Checks whether an object is one of the item in the list.
    This is different from ``in`` because ``in`` uses __cmp__ when
    present. Here we change based on the object itself
    """
    for item in l:
        if item is obj:
            return True
    return False