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test_itertools.py does not test infinite iterable for itertools.chain.from_iterable #93814

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youknowone opened this issue Jun 14, 2022 · 2 comments · Fixed by #93815
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test_itertools.py does not test infinite iterable for itertools.chain.from_iterable #93814

youknowone opened this issue Jun 14, 2022 · 2 comments · Fixed by #93815
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@youknowone youknowone commented Jun 14, 2022

Bug report

itertools.chain.from_iterable is safe to use with infinite iterable, but no test exists.

example:

chain.from_iterable(repeat(range(5)))

Your environment

  • CPython versions tested on:
    3.10.4 and current main branch

  • Operating system and architecture:
    N/A
@youknowone youknowone added the type-bug label Jun 14, 2022
@youknowone youknowone mentioned this issue Jun 14, 2022
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@AlexWaygood AlexWaygood added the tests label Jun 14, 2022
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@rhettinger rhettinger commented Jun 14, 2022

ISTM there is no point in adding another test for this. Infinite iterators a just a special case of "bigger than you can reasonably consume".

From a consumers point of view, there is no way to differentiate an infinite iterator from a huge iterator (c.f. the halting problem).

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@youknowone youknowone commented Jun 14, 2022 •
edited

The test will prevent a potential regression to evaluate given iterable before consuming.

Please let me know if there is a test already covers a huge iterator.
I found test_long_chain_of_empty_iterables is a similar one, but it doesn't fully prevent it.

ref: RustPython/RustPython#3787

miss-islington pushed a commit that referenced this issue Jun 14, 2022
@youknowone
gh-93814: Add infinite test for itertools.chain.from_iterable (GH-93815)
274769c 
fix #93814

Automerge-Triggered-By: GH:rhettinger
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gh-93814: Add infinite test for itertools.chain.from_iterable youknowone/cpython
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@youknowone @rhettinger @AlexWaygood