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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Distinguishing between maildir, mbox, and MH files/directories?
Date: Sun, 31 Aug 2014 17:02:32 -0400
References: <20140831134525.25a4321e@bigbox.christie.dr>
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On 8/31/2014 2:45 PM, Tim Chase wrote:
> Tinkering around with a little script, I found myself with the need
> to walk a directory tree and process mail messaged found within.
> Sometimes these end up being mbox files (with multiple messages
> within), sometimes it's a Maildir structure with messages in each
> individual file and extra holding directories, and sometimes it's a
> MH directory.  To complicate matters, there's also the possibility of
> non-{mbox,maildir,mh) files such as binary MUA caches appearing
> alongside these messages.

I know nothing about the format within such file but will make a couple=20
of assumptions.

> Python knows how to handle each just fine as long as I tell it what
> type of file to expect.

By instantiating mailbox.mbox or mailbox.Maildir

>  But is there a straight-forward way to
> distinguish them?  (FWIW, the *nix "file" utility is just reporting
> "ASCII text", sometimes "with very long lines", and sometimes
> erroneously flags them as C or C++ files=E2=80=BD).

> All I need is "is it maildir, mbox, mh, or something else" (I don't
> have to get more complex for the "something else") inside an os.walk
> loop.

Simple method: try to parse with mbox and then Maildir and if either=20
succeeds, assume that the file was in the corresponding format.

try:
   <process as mbox>
except mailbox.FormatError:
   try:
     <process as Maildir>
   except mailbox.FormatError:
     pass

If a format is detectable in the first line or two, you could try to=20
write a detect(path) that would return the corresponding class.  That=20
would perhaps be a good addition to the mailbox module.  On the other=20
hand, if you are interested in just those two classes, and not any of=20
the Maildir subclasses, the above might be good enough. I am assuming=20
that FormatError is raised without reading the whole file and doing a=20
lot else before detecting the mismatch.

--=20
Terry Jan Reedy