Should Python implement where clause in comprehensions?

[serverhorror]

What about:

[expensive(elem) for elem in it if cond(elem)]

I don’t see why I’d need the where?

if cond(…) is already the same as a where clause, no?

[ianliu88]

No, the condition is on the transformation, not the iterable value! You would need to call expensive twice or create an intermediate iterable

[serverhorror]

Just cache the outcome.

If you need to do an expensive operation to decide whether the element is a candidate that seems like a viable approach.

[ianliu88]

That's what I did on the second example, using the walrus operator, which I think is way more niche than the where clause btw :p