Question

Looking for a way to simulate nested loops (or a cartesian product) i came across the itertools.product function.
i need a function or piece of code that receive a list of integers as input and returns a specific generator.

example:
input = [3,2,4] -> gen = product(xrange(3),xrange(2),xrange(4))
or
input = [2,4,5,6] -> gen = product(xrange(2),xrange(4),xrange(5),xrange(6))

as the size of the lists varies i am very confused in how to do that without the need of a lot of precoding based on a crazy amount of ifs and the size of the list.

also is there a difference in calling product(range(3)) or product(xrange(3))?

Answer 1

def bigproduct(*args):
  newargs = [xrange(x) for x in args]
  return itertools.product(*newargs)

for i in bigproduct(3, 2, 4):
   ....

range() generates a list up-front, therefore uses time up front and more space, but takes less time to get each element. xrange() generates each element on the fly, so takes up less space and initial time, but takes more time to return each element.