Richie Hindle <richie at entrian.com> writes:
>[Cameron]>> Whenever you feel like a lambda, define a named function; >[Kyler]>> How do you cleanly do that?>> foo = range(-10, 10)>> my_op = lambda x: float(x) / max(map(abs, foo))>> bar = map(my_op, foo)>foo = range(-10, 10)>def my_op(x):> return float(x) / max(map(abs, foo))>bar = map(my_op, foo)>...did I misunderstand?
Well, your solution depends on a global variable. That's going to
get *really* ugly if we move beyond the trivial example given here.
There are other problems but they're apparently not obvious with
How 'bout some non-working code to shine some more light on it? (If
pressed, I should be able to come up with similar code that works!)
def make_translation_function(GCPs, type, invert=False):
if type == 'LSF' and len(GCPs) < 12:
# Do lots of time-consuming magic to calculate A, B, ...
lambda x, y: (
x * A + y * B +
x * y * C +
x * G + y * H +
x * y * I +
elif ... # Repeat lots of times for variations.
map_im = foo.open('map.tif')
map_translation = make_translation_function(map_im.get_GCPs, type='LSF')
path_im = foo.open('path.tif')
path_translation_i = make_translation_function(path_im.get_GCPs, type='LSF', invert=True)
# Mark all points on map that are red in path.
for (x, y) in all_red_pixels(path_im):
(lon, lat) = path_translation_i(x, y)
(x, y) = map_translation(lon, lat)
map_im.putpixel((x, y), mark_val)
Now, let's pretend that this is part of a larger program that's doing lots
of things with, potentially, lots of images, and let's also say that we
allow user-defined/imported extensions to make_translation_function().
How are you going to make a *clean* solution using named functions?