Why dask delayed do nothing?

Question

I am using dask to process files line by line. However, dask seems that do not do anything. My code logic is as follows:

import dask
from dask import delayed
from time import sleep

@dask.delayed
def inc(x):
    sleep(1)
    print(x)


def test():
    for i in range(5):
        delayed(inc)(i)

dask.compute(test())

However, no any outputs in console. Why?

score 2 · Accepted Answer · answered Apr 29 '20 at 12:37

2

Your function test does not return anything.

Perhaps you meant to do something like

def test():
    out = []
    for i in range(5):
        out.append(inc(i))
    return out

(note that you already decorated inc with delayed, there is no need to call delayed(inc) again)

answered Apr 29 '20 at 12:37

mdurant

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So if the function does not return anythin, then dask would not run the function. Thanks, I successfully run the function! – DuFei Apr 30 '20 at 01:24
1

I would rather say: you gave `compute()` nothing to do. – mdurant Apr 30 '20 at 12:33

Why dask delayed do nothing?

1 Answers1