Possible Addition to Python Language: Marked Sub-condition

[Terry Reedy]

On 3/8/2020 12:07 PM, MRAB wrote:

> In Python 3.8+ there's the "walrus operator" which lets you assign 
> within an expression:
> 
> if (first := (color == BLUE and count == 20)) or (second := (color == 
> RED and count % 5 == 0)):
>      rotate_the_wheel()
>      if first:
>          set_signal()
>      if second:
>          unset_signal()
>       proc_post_rotate()
> 
> However, this has the problem that if the first subexpression is true, 
> the second will not be evaluated, so 'second' would not be set.

One can use '|' instead of 'or' to force evaluation of the second.

 >>> if (first := True) | (second := False):
	second
	
False


-- 
Terry Jan Reedy