[New-bugs-announce] [issue26293] Embedded zipfile fields dependent on absolute position

[spoo]

New submission from spoo:

Example:

from zipfile import ZipFile
with open('a.zipp', 'wb') as base:
    base.write(b'old\n')
    with ZipFile(base, 'a') as myzip:
        myzip.write('eggs.txt')

If the embedded zip portion of the file is extracted (first four bytes deleted), some fields will be incorrect in the resultant file - commenting out line 3 produces a file that can serve as a comparison.  These differences cause issues opening with some zip library implementations.

My best guess is that this is related to this line: https://github.com/python/cpython/blob/master/Lib/zipfile.py#L1459

----------
components: Library (Lib)
messages: 259642
nosy: spoo
priority: normal
severity: normal
status: open
title: Embedded zipfile fields dependent on absolute position
type: behavior
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26293>
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