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Minor optimizations by using comprehensions #182

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@cclauss cclauss commented Apr 28, 2024

% ruff check --select=C4,PERF --ignore=PERF203

pyperf/__main__.py:355:21: PERF401 Use a list comprehension to create a transformed list
pyperf/_bench.py:563:21: PERF401 Use a list comprehension to create a transformed list
pyperf/_compare.py:168:13: PERF401 Use a list comprehension to create a transformed list
pyperf/_compare.py:253:21: C414 Unnecessary `list` call within `sorted()`
pyperf/_compare.py:285:13: PERF401 Use a list comprehension to create a transformed list
pyperf/_compare.py:432:13: PERF401 Use a list comprehension to create a transformed list
pyperf/_cpu_utils.py:94:17: PERF402 Use `list` or `list.copy` to create a copy of a list
pyperf/_utils.py:133:21: PERF402 Use `list` or `list.copy` to create a copy of a list
pyperf/tests/test_bench.py:351:13: PERF401 Use a list comprehension to create a transformed list
Found 9 errors.

% ruff rule PERF401

manual-list-comprehension (PERF401)

Derived from the Perflint linter.

What it does

Checks for for loops that can be replaced by a list comprehension.

Why is this bad?

When creating a transformed list from an existing list using a for-loop,
prefer a list comprehension. List comprehensions are more readable and
more performant.

Using the below as an example, the list comprehension is ~10% faster on
Python 3.11, and ~25% faster on Python 3.10.

Note that, as with all perflint rules, this is only intended as a
micro-optimization, and will have a negligible impact on performance in
most cases.

Example

original = list(range(10000))
filtered = []
for i in original:
    if i % 2:
        filtered.append(i)

Use instead:

original = list(range(10000))
filtered = [x for x in original if x % 2]

If you're appending to an existing list, use the extend method instead:

original = list(range(10000))
filtered.extend(x for x in original if x % 2)

@cclauss cclauss force-pushed the ruff-rules-PERF-and-C4 branch from de63bdf to 7713156 Compare April 28, 2024 13:05
@cclauss cclauss force-pushed the ruff-rules-PERF-and-C4 branch from 7713156 to 37eefd3 Compare April 28, 2024 13:16
@corona10
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ditto: #183 (comment)

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@vstinner vstinner left a comment

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I dislike this change. I don't think that these "micro optimizations" are worth it.

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I suggest to ignore this recommendation instead of trying to address it just because ruff thinks that the code is slow.

@cclauss cclauss closed this Apr 29, 2024
@cclauss cclauss deleted the ruff-rules-PERF-and-C4 branch April 30, 2024 20:37
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3 participants