From: | Daniele Varrazzo <daniele(dot)varrazzo(at)gmail(dot)com> |
---|---|
To: | Jan Urbański <wulczer(at)wulczer(dot)org> |
Cc: | Psycopg List <psycopg(at)postgresql(dot)org> |
Subject: | Re: psycopg2.connect change from a C function to module method |
Date: | 2011-12-28 12:26:24 |
Message-ID: | CA+mi_8Y_4arnxc-PXbLoPhkne8VqbrUK4NK_ffXiReAvDaawNQ@mail.gmail.com |
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Lists: | psycopg |
2011/12/27 Jan Urbański <wulczer(at)wulczer(dot)org>:
> Hi,
>
> the change that made psycopg2.connect a module-level Python function
> rather than a function exposed from a C module turned ou to be
> backwards-incompatible.
>
> Attached is a small snippet that works well with psycopg2 2.4.2 and
> tracebacks with "TypeError: argument 1 must be string, not C" with 2.4.3.
Uhm... if you assign a function to a class you get an unbound method:
this is the standard Python semantic. The fact it doesn't happen with
a C function seems just short of a cpython bug, and it's an ugly
asymmetry anyway.
> The potential for actual breakage is very small, but I wanted to report
> it in case someone hits it like I did and perhaps to discuss whether the
> fix I applied is correct.
I would have probably guarded it with an "if isinstance(conn,
types.UnboundMethodType)": because a C function doesn't become a
method, being able to make a staticmethod out of it seems a bet.
Even better, probably:
class C(object):
def conn(self, *args, **kwargs):
return psycopg2.connect(*args, **kwargs)
def __init__(self):
self.conn('')
to give subclasses the possibility to change it in a standard OOP way.
-- Daniele
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