布尔运算符的python扩充分配

Question

Does Python have augmented assignment statements corresponding to its boolean operators?

For example I can write this:

x = x + 1

or this:

x += 1

Is there something I can write in place of this:

x = x and y

To avoid writing "x" twice?

Note that I'm aware of statements using &= , but I was looking for a statement that would work when y is any type, not just when y is a boolean.

Answer 1

The equivalent expression is &= for and and |= for or .

>>> b = True
>>> b &= False
>>> b
False

Note bitwise AND and bitwise OR and will only work (as you expect) for bool types. bitwise AND is different than logical AND for other types, such as numeric

>>> bool(12) and bool(5)   # logical AND
True

>>> 12 & 5    # bitwise AND
4

Please see this post for a more thorough discussion of bitwise vs logical operations in this context.

Answer 2

No, there is no augmented assignment operator for the boolean operators .

Augmented assignment exist to give mutable left-hand operands the chance to alter the object in-place, rather than create a new object. The boolean operators on the other hand cannot be translated to an in-place operation; for x = x and y you either rebind x to x , or you rebind it to y , but x itself would not change.

As such, x and= y would actually be quite confusing; either x would be unchanged, or replaced by y .

Unless you have actual boolean objects, do not use the &= and |= augmented assignments for the bitwise operators . Only for boolean objects (so True and False ) are those operators overloaded to produce the same output as the and and or operators. For other types they'll either result in a TypeError , or an entirely different operation is applied. For integers, that's a bitwise operation, sets overload it to do intersections.