[Zope-dev] Fwd: Multi-argument append() is illegal

[Martijn Pieters]

From: "Patrick Phalen" <zope@teleo.net>
> Fredrik Lundh has mentioned that this breaks Zope (and Medusa).
>
> If so, it's probably not too soon to begin looking into it. 1.6 is due
> this summer.
>
>
> ----------  ## Forwarded Message ##  ----------
> Subject: Multi-argument append() is illegal
> Date: Mon, 28 Feb 2000 10:41:02 -0500
> From: Guido van Rossum <guido@python.org>
>
>
> I've noticed that there is some code out there that creates a list of
> tuples and uses code like list.append(a,b,c) to add the tuple (a,b,c)
> to the list.  According to the documentation, this is illegal:
> append() only takes a single argument, and one should write
> list.append((a,b,c)).  However, the actual append() implementation
> didn't mind, and implemented list.append(a,b,c) as
> list.append((a,b,c)).  Many people are using this even though it's
> never been documented.
>
> I am going to rectify this in Python 1.6 -- people coming from other
> languages might well expect list.append(a, b, c) to mean the same as
> list.append(a); list.append(b); list.append(c), and it's always been
> my philosophy to make ambiguous syntax illegal rather than to pick one
> interpretation randomly.
>
> This message is simply a heads-up that you should be aware of this
> change (when 1.6 comes out, which should be before the summer).  You
> can test your programs using the current CVS version (see
> www.python.org/download/cvs.html).  You can also grep through your
> sources for a pattern like "\. *append *\(.*," -- which doesn't find
> every occurrence, but is a good starting point.  If you have a smarter
> grep-like tool you may be able to write a tighter matching expression.
>
> Watch out for false hits though: some classes define their own
> multi-argument append()...
>
> --Guido van Rossum (home page: http://www.python.org/~guido/)

Using a more advanced pattern (one that weeds out most proper appends, and
takes multiple lines into account), plus some hand weeding, brings up the
following list of 'illegal' tuple appends:

lib\python\ExportImportXML.py(109):
    self._tindex.append(self._oid, here)
lib\python\Shared\DC\ZRDB\RDB.py(199):
    parsers.append(i,parser)
lib\python\Shared\DC\xml\ppml.py(278):
    def __setitem__(self, k, v): self._d.append(k,v)
lib\python\ZODB\FileStorage.py(633):
    self._tappend(oid, here)
lib\python\ZPublisher\cgi.py(603):
    r.append(name, value)
utilities\FS.py(145):
    self._tappend(oid, here)
ZServer\HTTPServer.py(285):
    request.channel.queue.append(self.module_name, zrequest, zresponse)
ZServer\medusa\asyncore.py(84):
    l.append (fd, flags)

Above 8 occurences are all cases of tuples being appended to a list, using
the 'illegal' style syntax. Note that I still may have missed occurences,
and that Python 1.6 might break other things. The change from 1.5.1 to 1.5.2
broke certain things in Zope as well, usually because of library changes.

For those of you that grok POSIX regexp, here is what I used to search these
out:

  append[[:blank:]]*\(([^[{(,]|[[:space:]])+,

where [:blank:] stands for whitespace (not including newlines), and
[:space:] is whitespace (including newline). This will miss aliasing of
.append (app=list.append), which I hunted out with a separate regexp, and
lines like:

  append(1 # number 1
         ,2 # number 2

which were again hunted (and none found) with another simple regexp. So I am
fairly sure I got em all =).

I have posted these to the Collector.

Martijn Pieters
| Software Engineer    mailto:mj@digicool.com
| Digital Creations  http://www.digicool.com/
| Creators of Zope       http://www.zope.org/
|   The Open Source Web Application Server
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