[Pypgsql-users] Quoting and UnQuoting strings for Bytea

[David H. <df...@fo...>]

Hello,

I'm in the process of extending an existing Python application that uses 
pySqlite to use postgreSQL with pypgsql as an alternative dbms (for use 
by up to 50 students simultaneously in a class) and nearly everything is 
working just fine.

I'm using bytea columns to store binary strings that are mainly cPickled 
strings and, in accordance with the pypgsql README I'm using:

PgQuoteBytea:    Escapes a string, which can contain NUL characters, so 
that it can used as an input to a bytea field.
PgUnQuoteBytea:    Reverses the action of PgQuoteBytea().

But these don't seem to be completely symmetrical. The quote function 
also encloses the whole string in single-quotes (why does it need to do 
this?) and any embedded single-quote characters are escaped as two 
single-quotes (documented as a security update in pypgsql  2.5) but 
neither of these are reversed by the unquote function.

I can work round this by using an construct like:

sout = PgSQL.libpq.PgUnQuoteBytea(bstring.value).replace("''","'")[1:-1]

but I'd like to check, first, if it's really necessary to do this - I 
may be  doing something  wrong somewhere, and second, is this a safe 
solution in the general case?

--
Regards,
David Hughes