Writing then reading in-memory bytes (BytesIO) gives a blank result

I wanted to try out the python BytesIO class.

As an experiment I tried writing to a zip file in memory, and then reading the bytes back out of that zip file. So instead of passing in a file-object to gzip, I pass in a BytesIO object. Here is the entire script:

    from io import BytesIO
    import gzip

    # write bytes to zip file in memory
    myio = BytesIO()
    g = gzip.GzipFile(fileobj=myio, mode='wb')
    g.write(b"does it work")

    # read bytes from zip file in memory
    g = gzip.GzipFile(fileobj=myio, mode='rb')
    result = g.read()


But it is returning an empty bytes object for result. This happens in both Python 2.7 and 3.4. What am I missing?

You need to seek back to the beginning of the file after writing the initial in memory file...


From: stackoverflow.com/q/26879981