Is there a more efficient threading lock?

[Barry Scott]

On 25/02/2023 23:45, Jon Ribbens via Python-list wrote:
> I think it is the case that x += 1 is atomic but foo.x += 1 is not.

No that is not true, and has never been true.

:>>> def x(a):
:...    a += 1
:...
:>>>
:>>> dis.dis(x)
  1           0 RESUME                   0

  2           2 LOAD_FAST                0 (a)
              4 LOAD_CONST               1 (1)
              6 BINARY_OP               13 (+=)
             10 STORE_FAST               0 (a)
             12 LOAD_CONST               0 (None)
             14 RETURN_VALUE
:>>>

As you can see there are 4 byte code ops executed.

Python's eval loop can switch to another thread between any of them.

Its is not true that the GIL provides atomic operations in python.

Barry