Is "... an object not iterable"? Error entering "x to y"?

Question

Consider the following two classes:

class Foo0(object):                                                 
    pass

class Foo1(object):
    def __contains__(self, _):
        return False

None of them are iterable, which can be seen by trying for i in Foo1(): pass:

Traceback (most recent call last):
   File "stuff.py", line 11, in <module>
    for i in Foo1(): pass
TypeError: 'Foo1' object is not iterable

And vice versa, it is 3 in Foo1()valid (as it Foo1has __contains__), while 3 in Foo0()not:

Traceback (most recent call last):
  File "stuff.py", line 9, in <module>
    3 in Foo0()
TypeError: argument of type 'Foo0' is not iterable

---

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Answer 1

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