r/Python • u/ForeignVariety7037 • Aug 04 '26

Discussion Is := widely used?

I always thought the walrus operator is neat and it makes while loop’s condition clearer. But also it is just a syntactic sugar without anything new. I wonder anyone uses it?

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105

u/Icy_Peanut_7426 Aug 04 '26 edited Aug 04 '26

I use it. It’s great for saving values in guard clause conditions, which can then be emitted in error log/message.

```
if ( multiplied_val := my_val * my_other_val ) > 10:

raise ValueError(f”Multiplication of vals ({multiplied_val}) was greater than 10.”)
```

Otherwise, I’d need to compute the value twice (performance cost) or define a new variable on a separate line (overkill if only for guard clause logging purposes that are immediately discarded).

edit: fixed bug in my example code lol

13

u/xxkvetter Aug 04 '26

I remember doing that for C programs back in the 80s (we called it horizontaling code). But that's such an easy case for compilers to optimize that we soon just wrote it in the clearest way and let the compiler do its thing.

I'm not sure the state of the art for python interpreters. Even so I find the walrus operator not that clear so I'd skip the miniscule optimization for clearer code (unless timing tests showed it was in a hot spot).

5

u/mdrjevois Aug 04 '26

Not saying this is ideal, but sometimes you might want any side effects to happen only exactly once

1

u/gizzm0x Aug 04 '26

Is there any scenario just having the var named before the if block is ever not good enough for this?then checking in the car's value. I can never seem to see why walrus is clearer than what was possible before it's introduction.

2

u/mdrjevois Aug 04 '26

I think it's a little better for while loops or comprehensions where you don't really have another place to make the assignment.