Re: problem with quoted strings while inserting into varchar field of database.
On 6 May 2007 11:22:52 -0700, Daniele Varrazzo [EMAIL PROTECTED] Every serious database driver has a complete and solid SQL escaping mechanism. This mechanism tipically involves putting placeholders in your SQL strings and passing python data in a separate tuple or dictionary. Kinda cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) I will try doing that once I get back to the lab. mean while I forgot to mention in my previous email that I use MySQLdb for python-mysql connection. I did not find any such reference to storing pickled objects in the API. any Idea what could be done with the mysql python module I am using? regards, Krishnakant. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On 7 Mag, 08:55, krishnakant Mane [EMAIL PROTECTED] wrote: On 6 May 2007 11:22:52 -0700, Daniele Varrazzo [EMAIL PROTECTED] Every serious database driver has a complete and solid SQL escaping mechanism. This mechanism tipically involves putting placeholders in your SQL strings and passing python data in a separate tuple or dictionary. Kinda cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) I will try doing that once I get back to the lab. mean while I forgot to mention in my previous email that I use MySQLdb for python-mysql connection. OK: MySQLdb implements the escaping mechanism i described. You can find the documentation if you look for it harder. I did not find any such reference to storing pickled objects in the API. Storing pickled object is not different from storing anything else into BLOB. You would have faced the same problem if you had to write O'Reilly in a VARCHAR field. -- Daniele -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On Mo, 7.05.2007, 10:30, Daniele Varrazzo wrote: On 7 Mag, 08:55, krishnakant Mane [EMAIL PROTECTED] wrote: On 6 May 2007 11:22:52 -0700, Daniele Varrazzo [EMAIL PROTECTED] Every serious database driver has a complete and solid SQL escaping mechanism. This mechanism tipically involves putting placeholders in your SQL strings and passing python data in a separate tuple or dictionary. Kinda cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) I will try doing that once I get back to the lab. mean while I forgot to mention in my previous email that I use MySQLdb for python-mysql connection. OK: MySQLdb implements the escaping mechanism i described. You can find the documentation if you look for it harder. I did not find any such reference to storing pickled objects in the API. Storing pickled object is not different from storing anything else into BLOB. You would have faced the same problem if you had to write O'Reilly in a VARCHAR field. -- Daniele -- http://mail.python.org/mailman/listinfo/python-list Why not use qmark parameter passing (PEP 249) ? cur.execute(INSERT INTO datatable (data) VALUES (?); , (pickled_data,)) Then the DB driver will take care for you. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On 7 Mag, 10:46, Stefan Sonnenberg-Carstens [EMAIL PROTECTED] wrote: On Mo, 7.05.2007, 10:30, Daniele Varrazzo wrote: On 7 Mag, 08:55, krishnakant Mane [EMAIL PROTECTED] wrote: On 6 May 2007 11:22:52 -0700, Daniele Varrazzo [EMAIL PROTECTED] Every serious database driver has a complete and solid SQL escaping mechanism. This mechanism tipically involves putting placeholders in your SQL strings and passing python data in a separate tuple or dictionary. Kinda cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) I will try doing that once I get back to the lab. mean while I forgot to mention in my previous email that I use MySQLdb for python-mysql connection. Why not use qmark parameter passing (PEP 249) ? cur.execute(INSERT INTO datatable (data) VALUES (?); , (pickled_data,)) Then the DB driver will take care for you. import MySQLdb print MySQLdb.paramstyle format MySQLdb (as many other drivers) use format parameter passing. Not much difference w.r.t. qmark, at least when passing positional parameters: the placeholder is %s instead of ?. A difference is that format also allows named parameters (actually it should have been pyformat, but IIRC MySQLdb can also use named placeholders, even if they advertise format). Anyway it is only a matter of placeholder style: they both allow the driver to take care of data escaping, the concept the OT didn't know about. -- Daniele -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On Mo, 7.05.2007, 11:32, Daniele Varrazzo wrote: On 7 Mag, 10:46, Stefan Sonnenberg-Carstens [EMAIL PROTECTED] wrote: On Mo, 7.05.2007, 10:30, Daniele Varrazzo wrote: On 7 Mag, 08:55, krishnakant Mane [EMAIL PROTECTED] wrote: On 6 May 2007 11:22:52 -0700, Daniele Varrazzo [EMAIL PROTECTED] Every serious database driver has a complete and solid SQL escaping mechanism. This mechanism tipically involves putting placeholders in your SQL strings and passing python data in a separate tuple or dictionary. Kinda cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) I will try doing that once I get back to the lab. mean while I forgot to mention in my previous email that I use MySQLdb for python-mysql connection. Why not use qmark parameter passing (PEP 249) ? cur.execute(INSERT INTO datatable (data) VALUES (?); , (pickled_data,)) Then the DB driver will take care for you. import MySQLdb print MySQLdb.paramstyle format MySQLdb (as many other drivers) use format parameter passing. Not much difference w.r.t. qmark, at least when passing positional parameters: the placeholder is %s instead of ?. A difference is that format also allows named parameters (actually it should have been pyformat, but IIRC MySQLdb can also use named placeholders, even if they advertise format). Anyway it is only a matter of placeholder style: they both allow the driver to take care of data escaping, the concept the OT didn't know about. -- Daniele -- http://mail.python.org/mailman/listinfo/python-list %s is not a placeholder IMHO. What happens when using %s is, that the string given will be inserted where %s is; that is something python does as with every print or such. By using the qmark style, it is up the the implementation of the cursor.execute method to decide what to do. python itself, and it's string implementation, don't know anything to do with the qmark. So, IMHO it *makes* a difference: with %s the execute function sees a string and nothing more as the parameters are consumed away by the % substitution. with ?, the execute implementation must do it's best, it gets a string and a list/tuple with values. Cheers, Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) %s is not a placeholder IMHO. What happens when using %s is, that the string given will be inserted where %s is; that is something python does as with every print or such. It is indeed. The behavior you describe would be true if i had used the % operator. Read better what i have written: There is no % operator. cur.execute() receives 2 parameters: a SQL string with placeholders and a tuple with values: it's not me mangling values into the SQL string. This is the driver responsibility and it has the chance because it receives SQL and values as two distinct parameters. The driver can ask the SQL string to contain placeholders either in qmark ? or in format %s style, but there is no functional difference. Notice that the placeholder is always %s and not %d or %f for integers or float: there is always an escaping phase converting each python object into a properly encoded string and then the placeholders are replaced with the value. This happens into the execute() machinery. By using the qmark style, it is up the the implementation of the cursor.execute method to decide what to do. python itself, and it's string implementation, don't know anything to do with the qmark. So, IMHO it *makes* a difference: with %s the execute function sees a string and nothing more as the parameters are consumed away by the % substitution. with ?, the execute implementation must do it's best, it gets a string and a list/tuple with values. Again, this would be true for cur.execute(sql % data): what i wrote is cur.execute(sql, data). -- Daniele -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On Mo, 7.05.2007, 16:26, Daniele Varrazzo wrote: cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) %s is not a placeholder IMHO. What happens when using %s is, that the string given will be inserted where %s is; that is something python does as with every print or such. It is indeed. The behavior you describe would be true if i had used the % operator. Read better what i have written: There is no % operator. cur.execute() receives 2 parameters: a SQL string with placeholders and a tuple with values: it's not me mangling values into the SQL string. This is the driver responsibility and it has the chance because it receives SQL and values as two distinct parameters. The driver can ask the SQL string to contain placeholders either in qmark ? or in format %s style, but there is no functional difference. Notice that the placeholder is always %s and not %d or %f for integers or float: there is always an escaping phase converting each python object into a properly encoded string and then the placeholders are replaced with the value. This happens into the execute() machinery. By using the qmark style, it is up the the implementation of the cursor.execute method to decide what to do. python itself, and it's string implementation, don't know anything to do with the qmark. So, IMHO it *makes* a difference: with %s the execute function sees a string and nothing more as the parameters are consumed away by the % substitution. with ?, the execute implementation must do it's best, it gets a string and a list/tuple with values. Again, this would be true for cur.execute(sql % data): what i wrote is cur.execute(sql, data). -- Daniele -- http://mail.python.org/mailman/listinfo/python-list Ashes on my head. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
Ashes on my head. My fault: the difference is hard to spot indeed in the rather long line of the example. I should have been more explicit stating that the differences were: 1. missing explicit quotes around the placeholders (they are part of the escaped values), 2. no % operator: two parameters are passed instead. Best regards, -- Daniele -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On Mon, 2007-05-07 at 07:26 -0700, Daniele Varrazzo wrote: cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) %s is not a placeholder IMHO. What happens when using %s is, that the string given will be inserted where %s is; that is something python does as with every print or such. It is indeed. The behavior you describe would be true if i had used the % operator. Read better what i have written: There is no % operator. This confusion is precisely why I think the (py)format paramstyles should be deprecated in a future version of the DB-API spec. Question marks make it immediately obvious that something other than string formatting is happening, and if I'm not mistaken, question marks are SQL standard. -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
On Mo, 7.05.2007, 16:50, Carsten Haese wrote: On Mon, 2007-05-07 at 07:26 -0700, Daniele Varrazzo wrote: cur.execute(INSERT INTO datatable (data) VALUES (%s);, (pickled_data,)) %s is not a placeholder IMHO. What happens when using %s is, that the string given will be inserted where %s is; that is something python does as with every print or such. It is indeed. The behavior you describe would be true if i had used the % operator. Read better what i have written: There is no % operator. This confusion is precisely why I think the (py)format paramstyles should be deprecated in a future version of the DB-API spec. Question marks make it immediately obvious that something other than string formatting is happening, and if I'm not mistaken, question marks are SQL standard. -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list At least, qmark style is well known to people working with prepared stmts etc. They look natural - and avoid (even my!) mistakes. On python-forum.de there was a discussion regarding inserting data into a sqlite db recently. If I remember correctly the guy was using the %s % data approach (yes, % operator) and failed. The pysqlite driver did the right thing using the qmark style. Even in the Python phrasebook there are examples of this ugly style. A deprecation warning for now would be fine. -- http://mail.python.org/mailman/listinfo/python-list
problem with quoted strings while inserting into varchar field of database.
hello, I finally got some code to push a pickled list into a database table. but now the problem is technically complex although possible to solve. the problem is that I can nicely pickle and store lists in a blob field with the help of dumps() for picklling into a string and then passing the string to the blob. I am also able to get back the string safely and do a loads() to unpickle the object. but this only works when list contains numbers. if there is a list such als lst = [a,b,c] then after a dumpls I get a pickled object into a string but when I try to insert this into the blob field it refuses to get into the table. there is an sql syntax error. I further discovered that the string variable that contains the pickled object contains a lot of single quots ' and this is what is probably preventing the sql insert from succedding. can some one suggest how to work around this problem? regards, Krishnakant. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with quoted strings while inserting into varchar field of database.
I further discovered that the string variable that contains the
pickled object contains a lot of single quots ' and this is what is
probably preventing the sql insert from succedding. can some one
suggest how to work around this problem?
Every serious database driver has a complete and solid SQL escaping
mechanism. This mechanism tipically involves putting placeholders in
your SQL strings and passing python data in a separate tuple or
dictionary. Kinda
cur.execute(INSERT INTO datatable (data) VALUES (%s);,
(pickled_data,))
instead of:
cur.execute(INSERT INTO datatable (data) VALUES ('%s'); %
(pickled_data,))
It is the driver responsibility to serialize the data (which usually
involves adding enclosing quotes and escape odd charaters such as
quotes themselves).
What database/driver are you using? PostgreSQL+psycopg2 or any other
wrong one? ;) In eiither case, read the driver documentation and the
DBAPI documentation (http://www.python.org/dev/peps/pep-0249/) for
further details.
-- Daniele
--
http://mail.python.org/mailman/listinfo/python-list
