Delete file from zipfile with the ZipFile Module

Question

The only way I came up for deleting a file from a zipfile was to create a temporary zipfile without the file to be deleted and then rename it to the original filename.

In python 2.4 the ZipInfo class had an attribute file_offset, so it was possible to create a second zip file and copy the data to other file without decompress/recompressing.

This file_offset is missing in python 2.6, so is there another option than creating another zipfile by uncompressing every file and then recompressing it again?

Is there maybe a direct way of deleting a file in the zipfile, I searched and didn't find anything.

Answer 1

The following snippet worked for me (deletes all *.exe files from a Zip archive):

zin = zipfile.ZipFile ('archive.zip', 'r')
zout = zipfile.ZipFile ('archve_new.zip', 'w')
for item in zin.infolist():
    buffer = zin.read(item.filename)
    if (item.filename[-4:] != '.exe'):
        zout.writestr(item, buffer)
zout.close()
zin.close()

If you read everything into memory, you can eliminate the need for a second file. However, this snippet recompresses everything.

After closer inspection the ZipInfo.header_offset is the offset from the file start. The name is misleading, but the main Zip header is actually stored at the end of the file. My hex editor confirms this.

So the problem you'll run into is the following: You need to delete the directory entry in the main header as well or it will point to a file that doesn't exist anymore. Leaving the main header intact might work if you keep the local header of the file you're deleting as well, but I'm not sure about that. How did you do it with the old module?

Without modifying the main header I get an error "missing X bytes in zipfile" when I open it. This might help you to find out how to modify the main header.