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author | Dylan Baker <dylan@pnwbakers.com> | 2017-05-01 15:11:01 -0700 |
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committer | Jussi Pakkanen <jpakkane@gmail.com> | 2017-05-02 21:57:26 +0300 |
commit | a8173630eac1f35914fdc2d918a636ac268b9033 (patch) | |
tree | c971b7e0be066df5a2a77f1141eb1517dd3903ef /ghwt.py | |
parent | ae924b01a006bc1542fe7eaae1d8a933459e8a0a (diff) | |
download | meson-a8173630eac1f35914fdc2d918a636ac268b9033.zip meson-a8173630eac1f35914fdc2d918a636ac268b9033.tar.gz meson-a8173630eac1f35914fdc2d918a636ac268b9033.tar.bz2 |
Don't use len() to test emptiness vs not emptiness
Meson has a common pattern of using 'if len(foo) == 0:' or
'if len(foo) != 0:', however, this is a common anti-pattern in python.
Instead tests for emptiness/non-emptiness should be done with a simple
'if foo:' or 'if not foo:'
Consider the following:
>>> import timeit
>>> timeit.timeit('if len([]) == 0: pass')
0.10730923599840025
>>> timeit.timeit('if not []: pass')
0.030033907998586074
>>> timeit.timeit('if len(['a', 'b', 'c', 'd']) == 0: pass')
0.1154778649979562
>>> timeit.timeit("if not ['a', 'b', 'c', 'd']: pass")
0.08259823200205574
>>> timeit.timeit('if len("") == 0: pass')
0.089759664999292
>>> timeit.timeit('if not "": pass')
0.02340641999762738
>>> timeit.timeit('if len("foo") == 0: pass')
0.08848102600313723
>>> timeit.timeit('if not "foo": pass')
0.04032287199879647
And for the one additional case of 'if len(foo.strip()) == 0', which can
be replaced with 'if not foo.isspace()'
>>> timeit.timeit('if len(" ".strip()) == 0: pass')
0.15294511600222904
>>> timeit.timeit('if " ".isspace(): pass')
0.09413968399894657
>>> timeit.timeit('if len(" abc".strip()) == 0: pass')
0.2023209120015963
>>> timeit.timeit('if " abc".isspace(): pass')
0.09571301700270851
In other words, it's always a win to not use len(), when you don't
actually want to check the length.
Diffstat (limited to 'ghwt.py')
-rwxr-xr-x | ghwt.py | 2 |
1 files changed, 1 insertions, 1 deletions
@@ -85,7 +85,7 @@ def install(sproj): return unpack(sproj, branch, sproj_dir) def run(args): - if len(args) == 0 or args[0] == '-h' or args[0] == '--help': + if not args or args[0] == '-h' or args[0] == '--help': print(sys.argv[0], 'list/install', 'package_name') return 1 command = args[0] |