BoppreH <[email protected]> added the comment:
I'm not sure this is a duplicate of issue29094. That issue includes random data
at the start of the file, while this issue uses the 'ab' mode solely for a
creating the file if it doesn't exist (and thus is either empty or already a
valid zip file). It's not clear to me why 'wb' should work but not 'ab' if the
file was empty/missing to begin with.
[Windows 10, Python 3.6.3, 64 bit] still has the same problem.
Here's a more complete test case, starting with no existing files:
from zipfile import ZipFile
# Append mode: v
with open('file.zip', 'ab') as f:
with ZipFile(f, 'a') as zip:
zip.writestr('file.txt', 'contents')
with open('file.zip', 'rb') as f:
with ZipFile(f, 'r') as zip:
print(zip.read('file.txt'))
# Fails with "zipfile.BadZipFile: Bad magic number for file
header"
# Write mode: v
with open('file.zip', 'wb') as f:
with ZipFile(f, 'a') as zip:
zip.writestr('file.txt', 'contents')
with open('file.zip', 'rb') as f:
with ZipFile(f, 'r') as zip:
print(zip.read('file.txt'))
# Works.
----------
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<https://bugs.python.org/issue30213>
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