New submission from liquidpele <[email protected]>:
reecepeg@3c22fb7d6b37 Pulpmill % python3 --version
Python 3.9.1
When buffering a small file, calling peek() can read in the entire underlying
thing and close it, so then following with a read() throws an error about the
file being closed already even though peek should not have that effect.
Reproducible Steps:
>>> r = BufferedReader(requests.get("https://google.com";, stream=True).raw)
>>> r.peek(2)[:2]
b'\x1f\x8b'
>>> r.peek()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: peek of closed file
>>> r.read()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: read of closed file
However, in the case of a larger stream it appears to work since the underlying
stream isn't closed yet:
>>> r = BufferedReader(requests.get("https://amazon.com";, stream=True).raw)
>>> r.peek(2)[:2]
b'\x1f\x8b'
>>> r.peek(2)[:2]
b'\x1f\x8b'
This seems inconsistent at best. Best I can tell, the issue is here and needs
to take the current buffer offset into account.
https://github.com/python/cpython/blob/main/Modules/_io/bufferedio.c#L845
----------
components: IO
messages: 397907
nosy: liquidpele
priority: normal
severity: normal
status: open
title: io.BufferedReader:peek() closes underlying file, breaking peek/read
expectations
versions: Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue44687>
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