python "in" operation comparing a string with a tuple of containing only 1 string

I notice a strange behavior of "in" operation when comparing a string with a tuple containing only 1 string.

'monday' in ('not monday')

the result is True
as if we were comparing 2 strings

but if I change the expression by adding another element in the tuple.

'monday' in ('not monday', 'not monday neither')

it returns False as expected.

any idea why?

>Solution :

>>> 'monday' in ('not monday')
True
>>> 'monday' in ('not monday',)
False

A single-element tuple must have the trailing comma. Otherwise, it gets interpreted as regular order-of-operations parentheses, which are meaningless in this case So, 'monday' in ('not monday') is syntatically identical to 'monday' in 'not monday'.