[Mailman-Developers] Python3 port of Mailman3

[Barry Warsaw]

On Nov 26, 2014, at 02:30 PM, Abhilash Raj wrote:

>I am working on porting mailman3 to python3. There are few doubts I have
>which may sound stupid, but I have a little knowledge about encoding and
>charsets which I think is important for the port. Also this is my first time
>working on python3 so forgive me for asking anything obvious( I did try
>googling first) The code is in very preliminary stages with tons of
>errors. Its up on launchpad.
>
>    lp:~raj-abhilash1/mailman/py3

Yay!  Note that I also have been playing around with it a bit.  I wouldn't say
it's a functional branch, but you might compare notes:

    lp:~barry/mailman/py3

>1. `pkg_resources.resource_string` used to read the configuration files while
>initialization and testing now returns bytes instead of string(like in
>python2).

Right.  "resource_string" is really a misnomer.  In another Python 3 project I
work on, I use:

from pkg_resource import resource_string as resource_bytes

just so that the call sites are accurate.

>So instead I use `pkg_resources.resource_stream` and deocode to the steam to
>a `utf-8` encoding(why? to avoid errors for the time being). I wanted to ask
>what would be the best for this case?

You can of course also decode the bytestring that "resource_bytes" returns.
That's generally what I do in that other project.

>2. To create a hash everywhere unicode strings must be encoded. So again the
>same question what should I encode it to? UTF-8 or US-ASCII? Or someway to
>determine which encoding should be used?

I think utf-8 is generally the right encoding to use, except in contexts where
you are given a better hint.  E.g. if you're decoding say the payload of a
message with a Content-Type header, and that header has a `charset` attribute,
it will name the encoding that you're supposed to use.

There may be cases where us-ascii or latin-1 would be better, but I think
those should be determined on a case-by-case basis.

>Also if anybody has suggestions on porting please let me know. I am online
>sporadically on irc as `maxking` on #mailman (I see all of the messages sent
>while I am away).

The trunk should now be `python2.7 -3` clean, so it's ready to be ported.
I'd probably not try to run the full test suite yet, but start at the lowest
level, e.g. database/model and work your way up.  If there are changes that
make sense even in Python 2 (i.e. for bilingual support for now) try to
put those in separate branches and merge proposals, so they can be merged into
trunk even before a full port.

This page will be indispensable:

https://wiki.python.org/moin/PortingToPy3k/BilingualQuickRef

Cheers,
-Barry
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