Priority of the logical statements NOT AND & OR in python

问题

As far as I know, in C & C++, the priority sequence for NOT AND & OR is NOT>AND>OR. But this doesn\'t seem to work in a similar way in Python. I tried searching for it in the Python documentation and failed (Guess I\'m a little impatient.). Can someone clear this up for me?

回答1:

It's NOT, AND, OR, from highest to lowest according to the documentation https://docs.python.org/3/reference/expressions.html#operator-precedence

Here is the complete precedence table, lowest precedence to highest. A row has the same precedence and chains from left to right

lambda
if – else
or
and
not x
in, not in, is, is not, <, <=, >, >=, !=, ==
|
^
&
<<, >>
+, -
*, /, //, %
+x, -x, ~x
**
x[index], x[index:index], x(arguments...), x.attribute
(expressions...), [expressions...], {key: value...}, {expressions...}

EDIT: Had the wrong precedence

回答2:

You can do the following test to figure out the precedence of and and or.

First, try 0 and 0 or 1 in python console

If or binds first, then we would expect 0 as output.

In my console, 1 is the output. It means and either binds first or equal to or (maybe expressions are evaluated from left to right).

Then try 1 or 0 and 0.

If or and and bind equally with the built-in left to right evaluation order, then we should get 0 as output.

In my console, 1 is the output. Then we can conclude that and has higher priority than or.

回答3:

not binds tighter than and which binds tighter than or as stated in the language reference

回答4:

Of the boolean operators the precedence, from weakest to strongest, is as follows:

or
and
not x
is not; not in

Where operators are of equal precedence evaluation proceeds from left to right.

回答5:

There is no good reason for Python to have other priority sequence of those operators than well established one in (almost) all other programming languages, including C/C++.

You may find it in The Python Language Reference, part 6.16 - Operator precedence, downloadable (for the current version and packed with all other standard documentation) from https://docs.python.org/3/download.html, or read it online here: 6.16. Operator precedence.

But there is still something in Python which can mislead you: The result of and and or operators may be different from True or False - see 6.11 Boolean operations in the same document.

来源：https://stackoverflow.com/questions/16679272/priority-of-the-logical-statements-not-and-or-in-python

标签

python

python-3.x

boolean-expression