Setting correct permissions on generated zip-file in Django

Question

I'm using Django and Python2.6 to generate a zip file of custom-rendered Django templates for each user to download a custom-made zip file. At the moment, the code in views.py looks like this:

def download(request):
    response = HttpResponse(mimetype='application/x-zip-compressed')
    response['Content-Disposition'] = 'attachment; filename=download.zip'

    myzip = zipfile.ZipFile(response, 'w')

    now = datetime.datetime.now()
    zipInfo = zipfile.ZipInfo('thefile.txt', (now.year, now.month, now.day, now.hour, now.minute, now.second))
    myzip.writestr(zipInfo, render_to_string('template.txt', locals(), context_instance=RequestContext(request)))
    myzip.close()

    return response

Mostly, this works fine: the zip file (containing a single txt file in this example) is downloaded correctly, and I can extract the contents. The only problem is, however, that the permissions on the generated file are neither read nor write for my default user, and neither will it be for my website users.

How do I change the permissions of the auto-generated file before download?

Update:

I've tried using os.chmod and os.fchmod, as suggested by Mike, but this either requires a path name (which I don't have) or gives an error (for fchmod):

ZipFile instance has no attribute '__trunc__'

One option, I guess, would be to save the zip file first, setting the permissions, and then allowing download, but that seems like overkill - there must be a better way to overcome this simple problem. Anyone have any suggestions or ideas?

Update2:

It seems this issue is limited to Unix systems, as it works fine in Windows and (apparently) OS X. There's a similar thread I found here. As far as I can tell, it must be related to the writestr method. How do I set the permissions on a file added to a zip file with writestr?

Answer 1

I think this is an issue with whatever you are using to extract the zip. The permissions seem fine to me:

zk@fool:~/Downloads% ls -l | grep thefile
-rwxr-xr-x@  1 zk  staff           9 May  3 06:37 thefile.txt*

Works fine for me with Archive Utility on osx and window's built-in zip explorer and 7-zip. Inspecting the generated zip shows files have no attributes at all. So I suspect whatever you are using to unzip the file is just setting permissions incorrectly.

You could try setting ZipInfo.external_attr:

zipInfo.external_attr = 0777 << 16L # set permissions on file

seems to fix the permissions on a linux system:

zk@arch:~% ls -l | grep thefile
-rwxrwxrwx  1 zk     9 May  3 07:06 thefile.txt*