Replace sequence concatination by unpacking in Airflow core

[hussein-awala]

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[hussein-awala]

More readable and fater:

$ python -m timeit '[1, 2, 3] + [4] + [5] + [6] + [7]'
2000000 loops, best of 5: 179 nsec per loop

$ python -m timeit '[*[1, 2, 3], 4, 5, 6, 7]'
5000000 loops, best of 5: 79 nsec per loop

[uranusjr]

I wonder if itertools.chain would be better here

[Lee-W]

I did some tests on it. It seems performance-wise [*[1, 2, 3], 4, 5, 6, 7] is the best solution

$ python -m timeit '[1, 2, 3] + [4] + [5] + [6] + [7]'
2000000 loops, best of 5: 179 nsec per loop

$ python -m timeit '[*[1, 2, 3], 4, 5, 6, 7]'
5000000 loops, best of 5: 69.2 nsec per loop

$ python -m timeit 'import itertools; itertools.chain([1, 2, 3], [4, 5, 6, 7])'
2000000 loops, best of 5: 177 nsec per loop

$ python -m timeit 'import itertools; [1, 2, 3] + [4] + [5] + [6] + [7]'
1000000 loops, best of 5: 242 nsec per loop

$ python -m timeit 'import itertools;  [*[1, 2, 3], 4, 5, 6, 7]'
2000000 loops, best of 5: 131 nsec per loop

$ python -m timeit 'import itertools; list(itertools.chain([1, 2, 3], [4, 5, 6, 7]))'
1000000 loops, best of 5: 305 nsec per loop

[uranusjr]

A big chunk of this would come from import itertools though, which would not be relevant in Airflow since the module is already imported in a lot of places. I would not be surprised if * is still best for small lists though, since the itertools version still needs to build an additional list (of a single item).

[Lee-W]

It looks good to me if @uranusjr 's suggestion is applied

[potiuk]

LGTM. I think using itertools for those is indeed over-the-top. I am fine witth the current version :)

[pierrejeambrun]

LGTM