Dom Grigonis writes:
This nuance can also be encountered in “principal use-case”. E.g.: class A: def func(self): while (self.a := 1) < 5: self.a += 1 return self.a
Not sure what you're getting at here, that's an infloop. Did you mean something like this: class A: def func(self): while (self.a := self.a += 1) < 5: pass return self.a I'm pretty sure that exact idiom, modeled on the C "copy string" idiom void strcpy(char *s, char *t) { while (*t++ = *s++) would generally be considered unpythonic, but I suppose some people might like it if instead of pass you had a real suite there. I think it's a real "meh" use case, since in most cases it can be rewritten class A: def func(self): while self.a < (5 - 1): # expression to make the # transformation clear self.a += 1 return self.a and you save a couple characters and at most one line (none in the case you present).
Same argument as for “walrus” operator itself - convenient feature. Or is there more to it?
There's more to it. The loop and a half construct, where you execute the body of the loop once outside the loop for some reason is widely considered a really big wart (DRY failure). The walrus allows us to eliminate most of those. On the other hand, an assignment and a return statement are two different things; it's not a DRY viotion to have the same identifier in both.
I was actually surprised that this didn’t work - I thought that this operator is a literal composite of assignment and “retriever", rather than having it’s own restrictive logic.
This is a common practice in Python development. Try a little bit of a new idea, avoid engineering, and expand later if that seems useful too.
If it doesn’t break anything, doesn’t have any undesirable side effects and community likes it, then could be a good addition.
"Community likes it" is a null predicate, very hard to verify in edge cases. When the support in the community is strong enough that "community likes it" is common knowledge, it's always the case that there are objective reasons why it's a good thing. All additions have a 0 * infinity cost: a negligible cost of learning (for one user) times *all* the users. Other projects feel differently about it, but Python tends to be quite conservative about additions. Steve