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Make sure that __dir__ returns new copies of __all__ #135

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Make sure that __dir__ returns new copies of __all__ #135

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2af5c69
Make sure that __dir__ returns a new copy of __all__
lagru Dec 10, 2024
df4f89a
Make linter happy
lagru Dec 10, 2024
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2 changes: 1 addition & 1 deletion lazy_loader/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ def __getattr__(name):
raise AttributeError(f"No {package_name} attribute {name}")

def __dir__():
return __all__
return list(__all__)
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Very minor nit: I prefer to use the copy method over a new constructor. As a reader, it tells me that __all__ is already a list and not being converted.

Suggested change
return list(__all__)
return __all__.copy()

On a more theoretical note (as these lists will generally be small enough to be negligible), using a method over a constructor permits the implementation to skip generic logic to handle multiple input types, so upstream optimizations in Python can potentially have higher impact.

Some timeit logs (py3.13) 
In [2]: _dir = dir()

In [4]: %timeit _dir[:]
41.7 ns ± 0.858 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

In [5]: %timeit list(_dir)
46.5 ns ± 0.816 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

In [6]: %timeit _dir.copy()
38.3 ns ± 0.667 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

In [9]: x = list(range(100000))

In [10]: %timeit list(x)
273 μs ± 12.1 μs per loop (mean ± std. dev. of 7 runs, 1,000 loops each)

In [11]: %timeit x.copy()
243 μs ± 8.06 μs per loop (mean ± std. dev. of 7 runs, 1,000 loops each)

In [12]: %timeit x[:]
231 μs ± 11.1 μs per loop (mean ± std. dev. of 7 runs, 1,000 loops each)

In [13]: x = list(range(1000))

In [14]: %timeit list(x)
1.13 μs ± 15 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [15]: %timeit x.copy()
1.13 μs ± 16 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [16]: %timeit x[:]
1.15 μs ± 16.9 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [17]: x = list(range(10))

In [18]: %timeit list(x)
36.3 ns ± 0.642 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

In [19]: %timeit x.copy()
26.5 ns ± 0.504 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

In [20]: %timeit x[:]
30.6 ns ± 0.748 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

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@lagru lagru Dec 10, 2024 •
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Yeah, I was debating that myself but chose to use list() over .copy() to be consistent with

lazy-loader/lazy_loader/__init__.py

Line 99 in 4e78314

return __getattr__, __dir__, list(__all__)

I'm happy to update both to .copy() if desired. 😊

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Sure, that's fine with me. Wasn't going to suggest it since it's a little out-of-scope, but I don't see the harm in changing it in passing.


if os.environ.get("EAGER_IMPORT", ""):
for attr in set(attr_to_modules.keys()) | submodules:
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23 changes: 23 additions & 0 deletions lazy_loader/tests/test_lazy_loader.py
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,29 @@ def test_lazy_attach():
assert locls[k] == v


def test_lazy_attach_returns_copies():
_get, _dir, _all = lazy.attach(
__name__, ["my_submodule", "another_submodule"], {"foo": ["some_attr"]}
)
assert _dir() is not _dir()
assert _dir() == _all
assert _dir() is not _all

expected = ["another_submodule", "my_submodule", "some_attr"]
assert _dir() == expected
assert _all == expected
assert _dir() is not _all

_dir().append("modify_returned_list")
assert _dir() == expected
assert _all == expected
assert _dir() is not _all

_all.append("modify_returned_all")
assert _dir() == expected
assert _all == [*expected, "modify_returned_all"]


def test_attach_same_module_and_attr_name():
from lazy_loader.tests import fake_pkg

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