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[Python-porting] Details about the psycopg porting

Antoine Pitrou solipsis at pitrou.net
Mon Jan 24 16:20:48 CET 2011 
Hello,

> I've written to the Psycopg mailing list about the details in the
> psycopg2 porting to Python 3. You can also read everything here:
> <http://initd.org/psycopg/articles/2011/01/24/psycopg2-porting-python-3-report/>.
> 
> There is a couple of points still open, so if you want to take a look
> at them I'd be happy to receive comments before releasing the code.

>From your article:

> the data (bytes) from the libpq are passed to file.write() using
> PyObject_CallFunction(func, "s#", buffer, len)”

You shouldn't use "s#" as it will implicitly decode the buffer to unicode.
Instead, use "y#" to write bytes.

> Is there an interface in Python 3 to know if a file is binary or text?

`isinstance(myfile, io.TextIOBase)` should do the trick. Or the corresponding C
call, using PyObject_IsInstance().

> In binary mode the file always returns bytes (str in py2, unicode in py3)

I suppose you mean "str in py2, bytes in py3".

> bytea fields are returned as MemoryView, from which is easy to get bytes

Is this because it is easier for you to return a memoryview? Otherwise it would 
make more sense to return a bytes object.

Regards

Antoine.
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