Getting the endpoints of sets across a range

For th开发者_开发技巧e life of me, I can't see how to do this. I need to collect the non-overlapping endpoints of several sets within a range of numbers with python.

For example the user could input a range of 10 and two sets 2 and 3. I need to get the end points of these sets within this range such that:

set 2 groupings: 1-2,6-7
set 3 groupings: 3-5,8-10

The range, number of sets, and size of any individual set is arbitrary. I cannot fall outside the range, so no half sets.

I keep thinking there should be a simple formula for this, but I can't come up with it.

Edit

As requested for an example input of range 12, and sets 1, 2, and 3 the output should be:

set 1: 1,7
set 2: 2-3,8-9
set 3: 4-6,10-12

As near as I can figure, I'm looking at some kind of accumulator pattern. Something like this psuedo code:

for each miniRange in range:
    for each set in sets:
        listOfCurrSetEndpoints.append((start, end))

I don't think there's a good built-in solution to this. (It would be easier if there were a built-in equivalent to Haskell's scan function.) But this is concise enough:

>>> import itertools
>>> from collections import defaultdict
>>> partition_lengths = [1, 2, 3]
>>> range_start = 1
>>> range_end = 12
>>> endpoints = defaultdict(list)
>>> for p_len in itertools.cycle(partition_lengths):
...     end = range_start + p_len - 1
...     if end > range_end: break
...     endpoints[p_len].append((range_start, end))
...     range_start += p_len
... 
>>> endpoints
defaultdict(<type 'list'>, {1: [(1, 1), (7, 7)], 2: [(2, 3), (8, 9)], 3: [(4, 6), (10, 12)]})

You can now format the endpoints dictionary for output however you like.

As an aside, I'm really confused by your use of "set" in this question, which is why I used "partition" instead.

I'm not exactly happy with it, but I did get a working program. If someone can come up with a better answer, I'll be happy to accept it instead.

import argparse, sys

if __name__ == "__main__":

    parser = argparse.ArgumentParser(description='Take a number of pages, and the pages in several sets, to produce an output for copy and paste into the print file downloader', version='%(prog)s 2.0')
    parser.add_argument('pages', type=int, help='Total number of pages to break into sets')
    parser.add_argument('stapleset', nargs='+', type=int, help='number of pages in each set')
    args = parser.parse_args()

    data = {}
    for c,s in enumerate(args.stapleset):
        data[c] = []

    currPage = 0
    while currPage <= args.pages:
        for c,s in enumerate(args.stapleset):
            if currPage + 1 > args.pages:
                pass
            elif currPage + s > args.pages:
                data[c].append((currPage+1,args.pages))
            else:
                data[c].append((currPage+1,currPage+s))
            currPage = currPage + s

    for key in sorted(data.iterkeys()):
        for c,t in enumerate(data[key]):
            if c > 0:
                sys.stdout.write(",")
            sys.stdout.write("{0}-{1}".format(t[0],t[1]))
        sys.stdout.write("\n\n")