Unzipping a .zip properly, and from a remote URL

[Christopher Culver]

Returning to Python after several years away, I'm working on a little
script that will download a ZIP archive from a website and unzip it to
a mounted filesystem. The code is below, and it works so far, but I'm
unsure of a couple of things.

The first is, is there a way to read the .zip into memory without the
use of a temporary file? If I do archive = zipfile.ZipFile(remotedata.read())
directly without creating a temporary file, the zipfile module
complains that the data is in the wrong string type.

The second issue is that I don't know if this is the correct way to
unpack a file onto the filesystem. It's strange that the zipfile
module has no one simple function to unpack a zip onto the disk. Does
this code seem especially liable to break?

    try:
        remotedata = urllib2.urlopen(theurl)
    except IOError:
        print("Network down.")
        sys.exit()
    data = os.tmpfile()
    data.write(remotedata.read())
    
    archive = zipfile.ZipFile(data)
    if archive.testzip() != None:
        print "Invalid zipfile"
        sys.exit()
    contents = archive.namelist()

    for item in contents:
        try:
            os.makedirs(os.path.join(mountpoint, os.path.dirname(item)))
        except OSError:
            # OSError means that the dir already exists, but no matter.
            pass
        if item[-1] != "/":
            outputfile = open(os.path.join(mountpoint, item), 'w')
            outputfile.write(archive.read(item))
            outputfile.close()