On Sun, 18 Dec 2011 15:04:13 -0500, Roy Smith wrote: > In article <jclflh$u45$1...@news.albasani.net>, > HoneyMonster <someone@someplace.invalid> wrote: > >> Hi, >> >> I'm just starting to learn Python, so please bear with me. I have in my >> program an object (recs) which is a list of tuples (returned as such by >> a database query). > > Sounds like a standard database interface -- each tuple represents one > row in the query result. Very common. > >> My question is doubtless a very easy one to answer: Say I want the >> ninth element in the twentieth tuple put into variable PID, I can do >> this, bearing in mind that numbering starts at zero: >> >> tup = recs[19] >> PID = tup[8] > > Sure, you could do: > > PID = recs[19][8] > > That's shorter, but it probably not better. Presumably, the tuple > elements represent columns in the database. It would make the code > easier to read if you unpacked the tuple into something with > human-readable names: > > col_1, col_2, col_3, ...... col_n = recs[19] > > and then use the name for the column of interest. A common convention > is that when you're unpacking a tuple (or a list, I suppose) and are > only interested in some of the elements, you unpack the others into "_". > Thus: > > _, _, _, _, pid, _, _, _ = recs[19] > > Of course, if you're going to do all that, you probably could have > written a better query which returned just the column you were > interested in. Instead of "select * from foo", you could have done > "select pid from foo" (assuming you're using some SQL-based database). > >> Secondly, I am more than happy to read the fine manuals. If someone >> could point me in the direction of one or two "for idiots" guides, that >> would be greatly appreciated. > > The on-line tutorial is pretty good. > http://docs.python.org/tutorial/index.html
Thanks, Arnaud and Roy. I had no idea it could be so easy. I think I rather like Python! OK, I'll change PID to pid if that's best practice. Yes, it's an SQL-based database, PostgreSQL actually. I'm using psycopg2 to access it and wxGlade to construct the GUI interface. It all seems to be progressing very smoothly. Thanks again. -- http://mail.python.org/mailman/listinfo/python-list
