On 02/25/2011 10:27 AM, Seldon wrote:
Hi all,
I have to convert integer ranges expressed in a popular "compact"
notation (e.g. 2, 5-7, 20-22, 41) to a the actual set of numbers (i.e.
2,5,7,20,21,22,41).
Is there any library for doing such kind of things or I have to write it
from scratch ?
In addition to the solutions given by others (thanks!), just for
reference I paste below what I have written to solve my little problem:
comments are welcome !
-------------------
# Define exceptions
class MalformedRangeListError(Exception): pass # raised if a string is\
not a valid numeric range list
def num_range_list_to_num_set(range_list, sep=','):
"""
Convert a numeric list of ranges to the set of numbers it represents.
@argument
range_list: a numeric list of ranges, as a string of values
separated by `sep` (e.g. '1, 3-5, 7')
@argument:
sep: a string used as a separator in `range_list` (e.g. ',', ' ')
@return: the set represented by `range_list` (i.e. (1,3,4,5,7)).
"""
# if given an empty range list, the function should return the\
empty set
if range_list == '': return set()
import re
int_or_range = r'^([1-9]\d*)(?:-([1-9]\d*))?$' # match a single
decimal number or a range of decimal numbers
r = re.compile(int_or_range)
# split the input string in a list of numbers and numeric ranges
l = range_list.split(sep)
result = set()
for s in l:
# check if the current string is a number or a valid numeric range
m = r.match(s)
if not m:
raise MalformedRangeListError, "Input string is not a valid
numeric range-list"
matches = len(filter(lambda x:x, m.groups())) # how many
regexp\ groups matched
first = m.group(1)
if matches == 2: # it's a range
if m.group(1) > m.group(2):
raise MalformedRangeListError, "Input string is not a\
valid numeric range-list"
last = m.group(2)
result.update(range(int(first), int(last)+1)) # current\
item is a range, so add the full numeric range to the result set
elif matches == 1: # it's a number
result.add(int(first)) # current item is a number, so just\
add it to the result set
else:
raise MalformedRangeListError, "Input string is not a valid
numeric range-list"
return result
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