Marko Rauhamaa wrote:
> Random832 <random...@fastmail.com>:
>
>> Sure, it's obvious to _me_ that << and >> have higher precedence than &
>> and |, and that "and" has a higher precedence than "or", but can I
>> assume the other people know this?
>
> No need to assume. Just read the spec:
>
> lambda Lambda expression
> if – else Conditional expression
> or Boolean OR
> and Boolean AND
> not x Boolean NOT
> in, not in, is, is not, <, <=, >, >=, !=, ==
> Comparisons, including membership tests and identity
> tests
> | Bitwise OR
> ^ Bitwise XOR
> & Bitwise AND
> <<, >> Shifts
> +, - Addition and subtraction
> *, @, /, //, % Multiplication, matrix multiplication division,
> remainder [5]
> +x, -x, ~x Positive, negative, bitwise NOT
> ** Exponentiation [6]
> await x Await expression
> x[index], x[index:index], x(arguments...), x.attribute
> Subscription, slicing, call, attribute reference
> (expressions...), [expressions...], {key: value...}, {expressions...}
> Binding or tuple display, list display, dictionary
> display, set display
>
> <URL: https://docs.python.org/3/reference/expressions.html#operat
> or-precedence>
>
>> [To keep this on-topic, let's assume that this discussion has a goal of
>> getting something along the lines of "always/sometimes/never use
>> "unnecessary" parentheses" into PEP7/PEP8. Speaking of, did you know
>> that C has lower precedence for the bitwise operators &^| than for
>> comparisons? That was something that tripped me up for a very long time
>> and undermined my confidence as to other aspects of the bitwise
>> operators]
>
> Yes, I happened to know that. Python's the same way.
It's not. From the page you linked to:
"""
Unlike C, all comparison operations in Python have the same priority, which
is lower than that of any arithmetic, shifting or bitwise operation.
"""
> However, no need to memorize. It's all there in the spec. Same as with
> stdlib functions. Keep checking the spec.
Nah, I usually try it in the interactive interpreter:
$ python3 -c 'print(1 < 3 & 2)'
True
$ echo 'main() { printf("%d\n", 1 < 3 & 2); }' | tcc -run -
0
(tcc invocation courtesy of google/stackoverflow)
> You *can* assume other people have read the spec. Even more importantly,
> you can assume the Python interpreter complies with the spec.
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