Question about email-handling modules

[Steven D'Aprano]

On Thu, 20 Dec 2007 09:31:10 +0000, Robert Latest wrote:

> 1. Why can I get the 'subject' and 'from' header field unsig the []
> notation, but not 'to'? When I print Message.keys I get a list of all
> header fields of the message, including 'to'. What's the difference
> between message['to'] and message.get('to')?

message['to'] looks up the key 'to', raising an exception if it doesn't 
exist. message.get('to') looks up the key and returns a default value if 
it doesn't exist.

See help(message.get) for more detail.


> 2. Why can't I call the get_payload() method on the message? What I get
> is this cryptic error: "AttributeError: Message instance has no
> attribute 'get_payload'". I'm trying to call a method here, not an
> attribute. It makes no difference if I put parentheses after get_payload
> or not. I looked into the email/Message module and found get_payload
> defined there.

All methods are attributes (although the opposite is not the case), so if 
a method doesn't exist, you will get an AttributeError.

The email.Message.Message class has a get_payload, but you're not using 
that class. You're using mailbox.UnixMailbox, which returns an instance 
of rfc822.Message which *doesn't* have a get_payload method.

Damned if I can work out how to actually *use* the email module to read 
an mbox mail box. I might have to RTFM :(

http://docs.python.org/lib/module-email.html
http://docs.python.org/lib/module-mailbox.html


*later*

Ah! The Fine Manual is some help after all. Try this:

# copied from http://docs.python.org/lib/mailbox-deprecated.html
import email
import email.Errors
import mailbox
def msgfactory(fp):
    try:
        return email.message_from_file(fp)
    except email.Errors.MessageParseError:
        # Don't return None since that will
        # stop the mailbox iterator
        return ''

fp = file('mymailbox', 'rb')
mbox = mailbox.UnixMailbox(fp, msgfactory)
for message in mbox:
    print message.get_payload()



But note that message.get_payload() will return either a string (for 
single part emails) or a list of Messages (for multi-part messages).


-- 
Steven