On 2009-03-07, Rhodri James <rho...@wildebst.demon.co.uk> wrote: > On Fri, 06 Mar 2009 15:34:08 -0000, Grant Edwards <inva...@invalid> wrote: > >> On 2009-03-06, Fencer <no.s...@plz.ok> wrote: >> >>> Hi, I need a boolean b to be true if the variable n is not >>> None and not an empty list, otherwise b should be false. >> >>> I ended up with: >> >>> b = n is not None and not not n >> >> I'd do it like this: >> >> b = (n is not None) and (n != []) > > The second comparison isn't actually necessary, since an > empty list is True and a non-empty one False. > > b = (n is not None) and n > > Putting the comparison in does make the code slightly less > "magic", though, so it's not a bad idea to do it!
Putting in the second comparison in makes the code match the stated requirement. Otherwise you have to start making assumptions about what n might be besides None or the empty list. -- Grant -- http://mail.python.org/mailman/listinfo/python-list
