How is the __contains__ method of the list class in Python implemented?

Question

Suppose I define the following variables:

mode = \"access\"
allowed_modes = [\"access\", \"read\", \"write\"]

I currently have a type check

Answer 1

No, they're not equivalent. For example:

>>> mode = float('nan')
>>> allowed_modes = [mode]
>>> any(mode == allowed_mode for allowed_mode in allowed_modes)
False
>>> mode in allowed_modes
True

See Membership test operations for more details, including this statement:

For container types such as list, tuple, set, frozenset, dict, or collections.deque, the expression x in y is equivalent to any(x is e or x == e for e in y).