[Email-SIG] Generating zipped or gzipped attachment with email package?

[Tony Nelson]

At 11:23 -0500 05/21/2009, skip at pobox.com wrote:
>(I posted this earlier to python-list at python.org then remembered we have an
>email package sig.  I hope it's ok to ask usage questions here...)
>
>I have a script which allows me to generate MIME messages with appropriate
>attachments.  It's essentially a lightly modified version of the second
>example from this page of the email package docs:
>
>    http://docs.python.org/library/email-examples.html
>
>I want to modify my script to automatically zip or gzip files which exceed
>some size threshold.  Doing the zip/gzip dance is no problem.  I'm concerned
>about how to specify that properly with the email package.  For example,
>consider a large CSV file.  I figure out the MIME type is text/csv.  Now
>suppose I gzip the file before attaching it.  How would this code change to
>specify the compression where "path" is now compressed?
>
>    if maintype == 'text':
>        fp = open(path)
>        # Note: we should handle calculating the charset
>        msg = MIMEText(fp.read(), _subtype=subtype)
>        fp.close()
>
>I guess I'm asking if I can have the Content-Type still be text/csv with
>some other MIME header indicating the file is compressed.  If so, how do I
>achieve that when attaching the compressed file to the message?

I think (untested):

    if maintype == 'text':
        fp = open(path)
        data = fp.read()
        fp.close()
        name = os.basename(path)
        if len(data) > datamax:
        #    do the zip/gzip compression to data
        #    set _subtype to 'zip' or 'x-gzip', or omit for octet-stream
            msg = MIMEApplication( data,
                _subtype='zip',
                _encoder=email.encoders.encode_base64,
                name=name )
        else:
            msg = MIMEText(data)
        del msg['Content-Disposition']   # paranoia
        msg.add_header('Content-Disposition',
            'attachment',   # or 'inline' and omit the name
            filename=name )

This will set the Content-Type: to "application/zip", reflecting the actual
type, encode to Base64 so the payload is ASCII, also setting the
Content-Transfer-Encoding, set a default name, and tell the MUA whether to
try to display the payload or save it as a file (also setting a default
name).
-- 
____________________________________________________________________
TonyN.:'                       <mailto:tonynelson at georgeanelson.com>
      '                              <http://www.georgeanelson.com/>