Expand a range which looks like: "1-3,6,8-10" to [1,2,3, 6, 8,9,10]

This function does what you asked. It assumes no negative numbers are used, otherwise it needs some changes to support that case.

def mixrange(s):
    r = []
    for i in s.split(','):
        if '-' not in i:
            r.append(int(i))
        else:
            l,h = map(int, i.split('-'))
            r+= range(l,h+1)
    return r


print mixrange('1-3,6,8-10')

One way using list comprehensions:

s = "1-3,6,8-10"
x = [ss.split('-') for ss in s.split(',')]
x = [range(int(i[0]),int(i[1])+1) if len(i) == 2 else i for i in x]
print([int(item) for sublist in x for item in sublist])

Outputs:

[1, 2, 3, 6, 8, 9, 10]

No builtin function as such, but can be done using xrange and generators:

from itertools import chain

s = "1-3,6,8-10"
spans = (el.partition('-')[::2] for el in s.split(','))
ranges = (xrange(int(s), int(e) + 1 if e else int(s) + 1) for s, e in spans)
all_nums = chain.from_iterable(ranges) # loop over, or materialse using `list`
# [1, 2, 3, 6, 8, 9, 10]