I had a quick question about the

.map

within prefect. Is it guaranteed that the order is preserved across multiple maps, like a python

multiprocessing.pool.map

? Or is it not a guarantee that the order is preserved, like

multiprocessing.pool.imap_unordered

. I couldn't find whether this was guaranteed or not in the

prefect docs

.

Hey @Kyle Hansen, is it not guaranteed. There is no priority ordering on the map.

So just to make sure, if I do a

func.map([a, b, c])

the result I get back might be

[result_b, result_c, result_a]

? I know they might not finish computing in the same order, but from my small scale tests, it seems I'm getting back

[result_a, result_b, result_c]

which I'm guessing is just an odd artifact of being lucky?

Oh that order of results in the list is guaranteed but the order of execution is not. So if you chain mapped tasks

a = A.map()

and

B.map(a)

, the output and input will connect as expected

Ah ok. Thanks for confirming that. This is kind of what I thought from my testing, but I wanted to make sure that was guaranteed. And I'm assuming that order is also preserved with a flat-mapping? So if I have

list = [[a, b, c], [d, e, f]]

and do a

func.map(flatten(list))

then my results back will be of the order

[result_a, result_b, result_c, result_d, result_e, result_f]

?

That one i’m not 100% sure. I’ll ask the team for you

Great. Thank you Kevin!!