Opening zipfile of unsupported compression-type silently returns empty filestream, instead of throwing exception

The cause is the combination of:

• this file's compression type is type 9: Deflate64/Enhanced Deflate (PKWare's proprietary format, as opposed to the more common type 8)
• and a zipfile bug: it will not throw an exception for unsupported compression-types. It used to just silently return a bad file object [Section 4.4.5 compression method]. Aargh. How bogus. UPDATE: I filed bug 14313 and it was fixed back in 2012 so it now raises NotImplementedError when the compression type is unknown.

A command-line Workaround is to unzip, then rezip, to get a plain type 8: Deflated.

zipfile will throw an exception in 2.7 , 3.2+ I guess zipfile will never be able to actually handle type 9, for legal reasons. The Python doc makes no mention whatsoever that zipfile cannot handle other compression types :(

My solution for handling compression types that aren't supported by Python's ZipFile was to rely on a call to 7zip when ZipFile.extractall fails.

from zipfile import ZipFile
import subprocess, sys

def Unzip(zipFile, destinationDirectory):
    try:
        with ZipFile(zipFile, 'r') as zipObj:
            # Extract all the contents of zip file in different directory
            zipObj.extractall(destinationDirectory)
    except:
        print("An exception occurred extracting with Python ZipFile library.")
        print("Attempting to extract using 7zip")
        subprocess.Popen(["7z", "e", f"{zipFile}", f"-o{destinationDirectory}", "-y"])