Quick nested loop syntax?

[Johannes Bauer]

Hi group,

if I remember correctly, wasn't there a way to quickly iterate through
nested loops? Something like

a = { "a", "b", "c" }
b = { 4, 9, 13}
for (x, y) in someoperator(a, b):
print(x, y)

which would print all tuples of
"a", 4
"a", 9
"a", 13
"b", 4
"b", 9
"b", 13
"c", 4
"c", 9
"c", 13

(not nececssarily in that order, of course).

Thanks,
Johannes

 

[Mark Dickinson]

Hi group,

if I remember correctly, wasn't there a way to quickly iterate through
nested loops? Something like

Python 2.6 has itertools.product:

http://docs.python.org/library/itertools.html#itertools.product

If you don't have Python 2.6 available, then the documentation
above also contains (almost) equivalent Python code that might
work for you.

Mark

 

[Terry Reedy]

Hi group,

if I remember correctly, wasn't there a way to quickly iterate through
nested loops? Something like

a = { "a", "b", "c" }
b = { 4, 9, 13}
for (x, y) in someoperator(a, b):
print(x, y)

from itertools import product
a = { "a", "b", "c" }
b = { 4, 9, 13}
for (x, y) in product(a, b):
print(x, y)

 

[alex23]

a = { "a", "b", "c" }
b = { 4, 9, 13}
for (x, y) in someoperator(a, b):
        print(x, y)

which would print all tuples of
"a", 4
"a", 9
"a", 13
"b", 4
"b", 9
"b", 13
"c", 4
"c", 9
"c", 13

If you're using a version of Python before 2.6, you could also use a
list comprehension:

show = lambda *args: sys.stdout.write('%s\n' % args)
[show((x,y)) for x in a for y in b]

('a', 4)
('a', 9)
('a', 13)
('b', 4)
('b', 9)
('b', 13)
('c', 4)
('c', 9)
('c', 13)