PEP 594: Removing dead batteries from the standard library

[mjpieters (Martijn Pieters)]

@xistence

cgi.FieldStorage is used to parse POST data, and backs all file storage inside WebOb.

As I understand it there are other frameworks that use it as well, such as Bottle.

I note that Werkzeug doesn’t use FieldStorage (or any other part of cgi, really). Django doesn’t use FieldStorage either, but do use cgi.parse_header and cgi.valid_boundary.

@xistence

cgi.parse_header is also used by Django and WebOb.

cgi.parse_multipart is used by Twisted.

Both of these functions should really be provided by the email package. There is an implementation of parse_header() in email.message.Message(), actually, so this functionality is duplicated across two different libraries in the standard lib:

>>> from cgi import parse_header
>>> from email.message import Message
>>> parse_header(h)
('application/json', {'charset': 'utf8'})
>>> m = Message()
>>> m['content-type'] = h
>>> m.get_params()
[('application/json', ''), ('charset', 'utf8')]
>>> m.get_param('charset')
'utf8'

cgi.parse_multipart() can likewise be handled by email.message; it’s all the same MIME RFC.

@xistence

If this PEP goes through and cgi.FieldStorage are not moved then anyone that is parsing multipart POST bodies will have to write their own, or copy an older version and hope they can get patches from other projects that have done the same.

Or someone creates a canonical package that everyone uses, just like they rely on Python’s cgi module. That’s not really an argument for or against removing cgi from the standard library. Moving it to PyPI does have the advantage that the fix you carry in WebOb could be upstreamed faster, you don’t have to wait for everyone to upgrade their Python installation first.

Note that both Werkzeug and Django already wrote their own POST data handling.