How to read from a zip file within zip file in Python?

Question

I have a file that I want to read that is itself zipped within a zip archive. For example, parent.zip contains child.zip, which contains child.txt. I am having trouble reading child.zip. Can anyone correct my code?

I assume that I need to create child.zip as a file-like object and then open it with a second instance of zipfile, but being new to python my zipfile.ZipFile(zfile.open(name)) is silly. It raises a zipfile.BadZipfile: "File is not a zip file" on (independently validated) child.zip

import zipfile
with zipfile.ZipFile("parent.zip", "r") as zfile:
    for name in zfile.namelist():
        if re.search(r'\.zip$', name) is not None:
            # We have a zip within a zip
            with **zipfile.ZipFile(zfile.open(name))** as zfile2:
                    for name2 in zfile2.namelist():
                        # Now we can extract
                        logging.info( "Found internal internal file: " + name2)
                        print "Processing code goes here"

Answer 1

When you use the .open() call on a ZipFile instance you indeed get an open file handle. However, to read a zip file, the ZipFile class needs a little more. It needs to be able to seek on that file, and the object returned by .open() is not seekable in your case. Only Python 3 (3.2 and up) produces a ZipExFile object that supports seeking (provided the underlying file handle for the outer zip file is seekable, and nothing is trying to write to the ZipFile object).

The workaround is to read the whole zip entry into memory using .read(), store it in a BytesIO object (an in-memory file that is seekable) and feed that to ZipFile:

from io import BytesIO

# ...
        zfiledata = BytesIO(zfile.read(name))
        with zipfile.ZipFile(zfiledata) as zfile2:

or, in the context of your example:

import zipfile
from io import BytesIO

with zipfile.ZipFile("parent.zip", "r") as zfile:
    for name in zfile.namelist():
        if re.search(r'\.zip$', name) is not None:
            # We have a zip within a zip
            zfiledata = BytesIO(zfile.read(name))
            with zipfile.ZipFile(zfiledata) as zfile2:
                for name2 in zfile2.namelist():
                    # Now we can extract
                    logging.info( "Found internal internal file: " + name2)
                    print "Processing code goes here"