New submission from Tyler Reddy <[email protected]>:
Downstream in NumPy we've noticed that a "sequence" object defined as below
will hang (infinite __getitem__ calls) if we try to turn it into an array. The
same holds in CPython for converting it to a list:
class OneList:
def __len__(self):
# this won't be checked by
# PySequence_Fast and several
# over C API calls
return 1
def __getitem__(self, x):
# called indefinitely by
# i.e., PySequence_Fast
return 1
Just to confirm -- this is intentional / desired behavior:
list(OneList()) should hang in CPython?
related:
https://github.com/numpy/numpy/issues/8912
https://github.com/numpy/numpy/pull/11815
https://stackoverflow.com/a/43566241/2942522
----------
messages: 324037
nosy: treddy
priority: normal
severity: normal
status: open
title: simple "sequence" class ignoring __len__
type: behavior
versions: Python 3.6
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<https://bugs.python.org/issue34494>
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