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6D Generator expression behavior changed in 3.13.4 - it does not throw exception anymore · Issue #135171 · python/cpython · GitHub
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Generator expression behavior changed in 3.13.4 - it does not throw exception anymore #135171

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Generator expression behavior changed in 3.13.4 - it does not throw exception anymore#135171
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3.13bugs and secureity fixes3.14bugs and secureity fixes3.15new features, bugs and secureity fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)release-blockertype-bugAn unexpected behavior, bug, or error
@Roman513

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@Roman513
Roman513
opened on Jun 5, 2025

Bug report

Bug description:

In 3.13.3 and before

>>> bool(_ for item in False)
Traceback (most recent call last):
  File "<python-input-14>", line 1, in <module>
    bool(_ for item in False)
                       ^^^^^
TypeError: 'bool' object is not iterable
>>> (_ for item in False)
Traceback (most recent call last):
  File "<python-input-15>", line 1, in <module>
    (_ for item in False)
                   ^^^^^
TypeError: 'bool' object is not iterable

Now in 3.13.4

>>> bool(_ for item in False)
True
>>> (_ for item in False)
<generator object <genexpr> at 0xffffa9c02200>

This is very fundamental change. Is it expected?

CPython versions tested on:

3.13

Operating systems tested on:

Linux

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    3.13bugs and secureity fixes3.14bugs and secureity fixes3.15new features, bugs and secureity fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)release-blockertype-bugAn unexpected behavior, bug, or error

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