How to convert numeric string ranges to a list in Python

Question

I would like to be able to convert a string such as \"1,2,5-7,10\" to a python list such as [1,2,5,6,7,10]. I looked around and found this, but I was wondering if there is a

Answer 1

Ugh, the answers are so verbose! Here is a short and elegant answer:

def rangeString(commaString):
    def hyphenRange(hyphenString):
        x = [int(x) for x in hyphenString.split('-')]
        return range(x[0], x[-1]+1)
    return chain(*[hyphenRange(r) for r in commaString.split(',')])

Demo:

>>> list( f('1,2,5-7,10') )
[1, 2, 5, 6, 7, 10]

Easily modifiable to handle negative numbers or return a list. Also will need from itertools import chain, but you can substitute sum(...,[]) for it if you are not working with range objects (or sum(map(list,iters),[])) and you don't care about being lazy.

Answer 2

This might be an overkill, but I just like pyparsing:

from pyparsing import *

def return_range(strg, loc, toks):
    if len(toks)==1:
        return int(toks[0])
    else:
        return range(int(toks[0]), int(toks[1])+1)
def parsestring(s):
    expr = Forward()
    term = (Word(nums) + Optional(Literal('-').suppress() + Word(nums))).setParseAction(return_range)
    expr << term + Optional(Literal(',').suppress() + expr)
    return expr.parseString(s, parseAll=True)

if __name__=='__main__':
    print parsestring('1,2,5-7,10')

Answer 3

No comprehension beats mine!

import re
def convert(x):
    return sum((i if len(i) == 1 else list(range(i[0], i[1]+1))
               for i in ([int(j) for j in i if j] for i in
               re.findall('(\d+),?(?:-(\d+))?', x))), [])

The best part is that I use variable i twice in the middle of the comprehension.

>>> convert('1,2,5-7,10')
[1, 2, 5, 6, 7, 10]

Answer 4

I was able to make a true comprehension on that question:

>>> def f(s):
    return sum(((list(range(*[int(j) + k for k,j in enumerate(i.split('-'))]))
         if '-' in i else [int(i)]) for i in s.split(',')), [])

>>> f('1,2,5-7,10')
[1, 2, 5, 6, 7, 10]

>>> f('1,3-7,10,11-15')
[1, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15]

the other answer that pretended to have a comprehension was just a for loop because the final list was discarded. :)

For python 2 you can even remove the call to list!

Answer 5

Very short, and elegant (imho):

>>> txt = "1,2,5-7,10"
>>> # construct list of xranges
>>> xranges = [(lambda l: xrange(l[0], l[-1]+1))(map(int, r.split('-'))) for r in txt.split(',')]
>>> # flatten list of xranges
>>> [y for x in xranges for y in x]
[1, 2, 5, 6, 7, 10]

Answer 6

def f(x):
    result = []
    for part in x.split(','):
        if '-' in part:
            a, b = part.split('-')
            a, b = int(a), int(b)
            result.extend(range(a, b + 1))
        else:
            a = int(part)
            result.append(a)
    return result

>>> f('1,2,5-7,10')
[1, 2, 5, 6, 7, 10]