test = [{'inf':1, 'numb':'11'},{'inf':1, 'numb':'99a'},{'inf':2, 'numb':'22'},{'inf':3, 'numb':'33'},{'inf':3, 'numb':'33`2a'},]
cu = {}
for i in test:
 if not cu.has_key(i['inf']):
    cu[i['inf']] = []
    cu[i['inf']].append(i['numb'])
 else:
    cu[i['inf']].append(i['numb'])

{1: ['11', '99a'], 2: ['22'], 3: ['33', '33`2a']}

from itertools import groupby
from operator import itemgetter

def foo():
    test = [{'inf':1, 'numb':'11'}, {'inf':1, 'numb':'99a'},
            {'inf':2, 'numb':'22'}, {'inf':3, 'numb':'33'},
            {'inf':3, 'numb':'33`2a'},
    ]
    test.sort(key=itemgetter("inf")) # если заранее известно, что test отсортирован по "inf", то можно не делать
    result = dict((k, [x["numb"] for x in g]) \
            for k, g in groupby(test, key=itemgetter("inf")))
    return result

from collections import defaultdict

def foo():
    test = [{'inf':1, 'numb':'11'}, {'inf':1, 'numb':'99a'},
            {'inf':2, 'numb':'22'}, {'inf':3, 'numb':'33'},
            {'inf':3, 'numb':'33`2a'},
    ]
    result = defaultdict(list)
    for i in test:
        result[i["inf"]].append(i["numb"])
    return result

{1: ['11', '99a'], 2: ['22'], 3: ['33', '33`2a']}

{1: ('11', '99a'), 2: '22', 3: ('33', '33`2a')}

street_number = {1: ['11', '99a'], 2: ['22'], 3: ['33', '33`2a']}

for v,k in street_number.items():
  if street_number.has_key(v):
	tpl.set_var("streets", v) #Это парсинг в переменную, самописный		
        sts=""
	for z in k:
	  if sts:
	     sts += ",'%s'" % z
	  else:
	     sts += "'%s'" % z
	 tpl.set_var("doma", sts)

var streets=new Array();
streets[{streets}] = new Array({doma});

streets[1]: ('11', '99a'), 
streets[2]:( '22'), 
streets[3]: ('33', '33`2a')}

>>> d = {1: ['11', '99a'], 2: ['22'], 3: ['33', '33`2a']}
>>> for i in d: d[i] = tuple(d[i])
... 
>>> d
{1: ('11', '99a'), 2: ('22',), 3: ('33', '33`2a')}
>>>