Use and meaning of "in" in an if statement?

Solution 1:

It depends on what next is.

If it's a string (as in your example), then in checks for substrings.

>>> "in" in "indigo"
True
>>> "in" in "violet"
False
>>> "0" in "10"
True
>>> "1" in "10"
True

If it's a different kind of iterable (list, tuple, set, dictionary...), then in checks for membership.

>>> "in" in ["in", "out"]
True
>>> "in" in ["indigo", "violet"]
False

In a dictionary, membership is seen as "being one of the keys":

>>> "in" in {"in": "out"}
True
>>> "in" in {"out": "in"}
False

Solution 2:

Using a in b is simply translates to b.__contains__(a), which should return if b includes a or not.

But, your example looks a little weird, it takes an input from user and assigns its integer value to how_much variable if the input contains "0" or "1".