Python equality statement of the form a==b in [c,d,e]

I just came across some python code with the following statement:

if a==b in [c,d,e]:
    ...

It turns out that:

>>> 9==9 in [1,2,3]
False
>>> 9==9 in [1,2,3,9]
True
>>> (9==9) in [1,2,3,9]
True
>>> 9==(9 in [1,2,3,9])
False
>>> True in [1,2,3,9]
True
>>> True in []
False
>>> False in []
False
>>> False in [1,2,3]
False

Am I right in assuming that a==b in [c,d,e] is equivalent to (a==b) in [c,d,e] and therefore only really makes sense if [c,d,e] is a list of True/False values?

And in the case of the code I saw b is always in the list [c,d,e]. Would it then be equivalent to simply using a==b?

Answer

Am I right in assuming that a==b in [c,d,e] is equivalent to (a==b) in [c,d,e]

No. Since both == and in are comparison operators, the expression

a == b in [c, d, e]

is equivalent to

(a == b) and (b in [c, d, e])

since all comparison operators have the same precedence but can be chained.

and therefore only really makes sense if [c,d,e] is a list of True/False values?

It can also make sense to check if a boolean value is contained in a list of integers. Since True is considered equivalent to 1, and False is considered equivalent to 0 (see The standard type hierarchy), the result of this check can even be True.