parse string of integer sets with intervals to list

Question

I have \"2,5,7-9,12\" string.

I want to get [2, 5, 7, 8, 9, 12] list from it.

Is there any built-in function for it in python?

Thanks.

Answer 1

This version handles arbitrary whitespace, overlapping ranges, out-of-order ranges, and negative integers:

from itertools import chain

def group_to_range(group):
  group = ''.join(group.split())
  sign, g = ('-', group[1:]) if group.startswith('-') else ('', group)
  r = g.split('-', 1)
  r[0] = sign + r[0]
  r = sorted(int(__) for __ in r)
  return range(r[0], 1 + r[-1])

def rangeexpand(txt):
  ranges = chain.from_iterable(group_to_range(__) for __ in txt.split(','))
  return sorted(set(ranges))


>>> rangeexpand('-6,-3--1,3-5,7-11,14,15,17-20')
[-6, -3, -2, -1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20]
>>> rangeexpand('1-4,6,3-2, 11, 8 - 12,5,14-14')
[1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 14]