Python Cookbook

Unpacking a Multipart MIME Message

Credit: Matthew Dixon Cowles

Problem

You have a multipart MIME message and want to unpack it.

Solution

The walk method of message objects generated by the email module (new as of Python 2.2) makes this task really easy:

import email.Parser
import os, sys

def main(  ):
    if len(sys.argv)==1:
        print "Usage: %s filename" % os.path.basename(sys.argv[0])
        sys.exit(1)

    mailFile = open(sys.argv[1], "rb")
    p = email.Parser.Parser(  )
    msg = p.parse(mailFile)
    mailFile.close(  )

    partCounter = 1
    for part in msg.walk(  ):
        if part.get_main_type(  )=="multipart":
            continue
        name = part.get_param("name")
        if name==None:
            name = "part-%i" % partCounter
        partCounter+=1
        # In real life, make sure that name is a reasonable filename 
        # for your OS; otherwise, mangle it until it is!
        f = open(name,"wb")
        f.write(part.get_payload(decode=1))
        f.close(  )
        print name

if _ _name_ _=="_ _main_ _":
    main(  )

Discussion

The email module, new in Python 2.2, makes parsing MIME messages reasonably easy. (See the Library Reference for detailed documentation about the email module.) This recipe shows how to recursively unbundle a MIME message with the email module in the easiest way, using the walk method of message objects.

You can create a message object in several ways. For example, you can instantiate the email.Message.Message class and build the message object’s contents with calls to its add_payload method. In this recipe, I need to read and analyze an existing message, so I worked the other way around, ...