[2,3,4,7] --> "2-4,7" ?

[andrew cooke]

(borrowing r hettinger's neat list comprehension):

import re
numb = re.compile('(\D*)(\d*)')

def group ((list, (last, start, end)), (next, num)):
    if last == next:
        if int(num) == int(end)+1: return (list, (last, start, num))
        if num == start: return (list, (next, num, num))
    return (list+[(last, start, end)], (next, num, num))

def fmt ((text, start, end)):
    if start == end: return text + start
    else: return text + start + "-" + end

def compare ((t1, n1), (t2, n2)):
    try: return cmp(t1, t2) or cmp(int(n1), int(n2))
    except: return 1

def tidy (list):
    if list:
        pairs = [numb.match(n).groups() for n in list]
        pairs.sort(compare)
        (text, num) = pairs[0]
        (groups, last) = reduce (group, pairs, ([], (text, num, num)))
        return map (fmt, groups+[last])
    else: return list

print tidy(['6','7','mx8','mx09','mx10','8','9','10','foo'])

andrew

-- 
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