Re: psycopg2.connect change from a C function to module method

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