Re: passing list values to an executemany cursor

Il giorno mar, 18/08/2009 alle 17.47 -0700, Peter Tittmann ha scritto:
[snip]
> insert_st='INSERT INTO pmh VALUES ('+frcs_o+')'
> cur.executemany(insert_st)
> 
> con.commit()
>    
> 
> The result is as follows:
>  >>> {'pmh_chainsaw': 84.031250000000014, 'pmh_loaderb': 
> 155.75707692307691, 'pmh_truck': 93.977430555555571, 'pmh_loaders': 
> 126.94655384615383}
> Traceback (most recent call last):
>   File "/tmp/py4195FHt", line 38, in <module>
>     insert_st='INSERT INTO pmh VALUES ('+frcs_o+')'
> TypeError: cannot concatenate 'str' and 'list' objects

This is a Python error, nothing related to psycopg. You're trying to
concatenate two strings and a list. Also this seems a simple INSERT to
me, why are you using executemany()?

> It appears that the connection is working and the lists have been 
> populated. I can check the db and see that the table has been created 
> with the appropriate column names. Any hints on correctly passing the 
> list falues from the 'frcs_o' list would be most gratefully recieved.

Supposing frcs_o contains a single row of values you can do :

insert_st = "INSERT INTO pmh VALUES (" + \
		",".join(["%s"]*len(frcs_names)) + ")"
cur.execute(insert_st, tuple(frcs_o))

The tricky part just generate the correct number of place holders for
the query statement. If, for example, len(frcs_names) is 3 you'll get:

INSERT INTO pmh VALUES (%s,%s,%s)

If and only if frcs_o is a list of tuples you can use executemany() to
insert more than one row at a time:

cur.executemany(insert_st, frcs_o)

Hope this helps,
federico

-- 
Federico Di Gregorio                         http://people.initd.org/fog
Debian GNU/Linux Developer                                [email protected]
INIT.D Developer                                           fog-NGVKUo/i/[email protected]
  Spesso crescere ed andare a vivere da soli è l'unico modo di restare
   bambini.                                             -- Alice Fontana

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