You should be using the and
operator instead for boolean operations.
Since python supports chaining relational operators (i.e. you can use 0 < var < 100
instead of 0 < var and var < 100
) and processes binary operations (i.e. addition, subtraction, bitwise operations, etc.) before relational operators due to operator precedence, all of the failing cases you posted actually mean something else.
var < 90 & var >= 80
is equivalent to (var < 90 & var) and (90 & var >= 80)
var < 90 & (var>=80)
is equivalent to var < 90 & True
for which look at the 4th case.
(var<90) & var>=80
is also similar to the 4th case (this resolves to True & var >= 80
which will then resolve to 0 >= 80
).
var < 90 & True
is equivalent to var < (90 & True)
. The implementation of the &
operator is designed to return 0
if either one of the operands is not an integer (which is another one of the biggest pitfalls of dynamic typing), which is why all such similar statements resolve to var < 0
which is false.
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