> On 2016-12-31 00:48, Deborah Swanson wrote: > >> On 30/12/16 23:00, Deborah Swanson wrote: > >> > Oops, indentation was messed up when I copied it into the email. > >> > Should be this: > >> > > >> > if len(l1[st]) == 0: > >> > if len(l2[st]) > 0: > >> > l1[st] = l2[st] > >> > elif len(l2[st]) == 0: > >> > if len(l1[st]) > 0: > >> > l2[st] = l1[st] > >> > >> That's even worse! > >> > >> Anyway, ignoring all that, if what you are trying to do is just do > >> some action based on a set of fixed comparisons that are known at > >> the top of > >> the function (and do not mutate depending on the path through the > >> function), then you can just cache the comparisons and then > >> compare the > >> resulting set of boolean results (note that my examples are > >> NOT based on > >> your use-case, it's just pseudo-code which happens to use > >> your expressions): > >> > >> state = (len(l1[st]) == 0, len(l2[st]) > 0) > >> if state == (True, False): > >> pass > >> elif state == (False, True): > >> pass > >> > >> ... etc. > >> > >> If the len() comparisons are tri-state (i.e., in some > cases you want > >> to know if the length is <, ==, or > 0, depending on one > of the other > >> comparisons) then you can do something like: > >> > >> def clamp(foo): > >> return min(max(-1, foo), 1) > >> > >> state = (clamp(cmp(len(l1[st]), 0), cmp(len(l2[st]), 0)) > >> if state == (0, -1): > >> pass > >> elif state == (1, -1): > >> pass > >> > >> ... etc. > >> > >> I'm not sure this makes it much more readable though - but if you > >> make the RHS of those comparisons a symbolic name you might be > >> getting somewhere - > >> > >> ACTION1 = (0, -1) > >> ACTION2 = (1, -1) > >> if state == ACTION1: > >> pass > >> elif state == ACTION2: > >> pass > >> > >> Hope that helps, E. > >> > > > > Thanks Erik, I really like your method of capturing the > state and then > > reusing it. I'm sure I can use it in other situations. In > this case, > > since I now have it down to: > > > > if not len(l1[st]) and len(l2[st]): > > l1[st] = l2[st] > > elif not len(l2[st]) and len(l1[st]): > > l2[st] = l1[st] > > > [snip] > > An empty list is considered falsey and a non-empty list is > considered truey: > > >>> bool([]) > False > >>> bool([0]) > True > > You don't care what the list's length is, only whether it's 0 > or not, so: > > if not l1[st] and l2[st]: > l1[st] = l2[st] > elif not l2[st] and l1[st]: > l2[st] = l1[st] >
Similar, actually the same as Cameron suggested. I really need to revisit testing for empty. I probably rejected it early on for some bad reason (you don't understand everything that goes wrong when you're learning). -- https://mail.python.org/mailman/listinfo/python-list
