Priority of operators: > and ==

Question

I'm trying to guess which operator has priority: > (greater than) or == (equal). This is my experiment:

>>> 5 > 4 == 1
False

As far as I know, this has two possible solutions.

>>> (5 > 4) == 1
True
>>> 5 > (4 == 1)
True

Neither one returns False, so how is the first code resolved by Python?

Answer 1

This has to do with operator chaining. Unlike C/C++ and most other languages, Python allows you to chain comparison operators just like you would in normal mathematics. From the documentation:

Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false).

So, this expression:

5 > 4 == 1

is actually interpreted as:

5 > 4 and 4 == 1  # Except that 4 is only evaluated once.

which becomes:

True and False

which is False.

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Using parenthesis however changes how Python interprets your comparison. This:

(5 > 4) == 1

becomes:

True == 1

which is True (see below for why). Same goes for:

5 > (4 == 1)

which becomes:

5 > False

which is also True.

---

Because of PEP 0285, bool was made a subclass of int and True == 1 while False == 0:

>>> issubclass(bool, int)
True
>>> True == 1
True
>>> False == 0
True
>>>