Question about email-handling modules

[Matt Nordhoff]

Robert Latest wrote:
> Hello,
> 
> I'm new to Python but have lots of programming experience in C, C++ and 
> Perl. Browsing through the docs, the email handling modules caught my eye 
> because I'd always wanted to write a script to handle my huge, ancient, and 
> partially corrupted email archives.
> 
> Of course I know that this kind of project shouldn't be tackled by a 
> beginner in a language, but I still thought I'd give it a spin. 
> 
> So I wrote the stuff at the bottom. It lists senders, subjects and 
> addressees of all messages in an mbox.
> 
> Things that I don't understand:
> 
> 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')?

On dicts, and presumably on Messages too, .get returns a default value
(None, or you can specify another with .get("key", "default") if the key
doesn't exist.

I can't say why ['to'] doesn't work when it's in the list of keys, though.

> 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. 

Methods are attributes. When you do "obj.method()", "obj.method" and
"()" are really two separate things: It gets the "method" attribute of
"obj", and then calls it.

> I don't want to waste your time by requesting that you pick apart my silly 
> example. But maybe you can give me a pointer in the right direction. This is 
> python 2.4 on a Debian box.
> 
> ---------------------------
> 
> #!/usr/bin/python
> import mailbox
> import email              # doesn't make a difference
> from email import Message # neither does this
> 
> mbox = file("mail.old/friends")
> 
> for message in mailbox.UnixMailbox(mbox):
>     subject = message['subject']
>     frm = message['from']
> #    to = message['to']         # this throws a "Key Error"
>     to = message.get('to');     # ...but this works
>     print frm, "writes about", subject, "to", to
> #    print message.get_payload() # this doesn't work
> 
> --------------------------
> 
> robert

(Oops, I wrote this like half an hour ago, but I never sent it.)
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