a = [ {"v": 52}, {"v": 94}, {"v": 75} ]

for v in a:
# или
for v in a[::-1]:
# или
[v for v in a if v['v'] == 52]

[dict(k=k,**v) for k,v in enumerate(a) if v['v'] == 94]

from itertools import count
a = [ {"v": 52}, {"v": 94}, {"v": 75} ]
c=count()
print [{"k":c.next(), "v":x["v"]} for x in a]

>>> a = [{"v": 52}, {"v": 94}, {"v": 75}, {"v": 75}]
>>> f = filter(lambda i: i[1]['v'] == 75, enumerate(a))
>>> f
[(2, {'v': 75}), (3, {'v': 75})]
>>> 
>>> a = [{"v": 52}, {"v": 94}, {"v": 75}, {"v": 75}]
>>> f = filter(lambda i: i[1]['v'] == 75, enumerate(a[::-1]))
>>> f
[(0, {'v': 75}), (1, {'v': 75})]
>>>

i[1]['v']

print a.index({"v": 75})

from operator import itemgetter
from functools import reduce
 
a = [ {"v": 52}, {"v": 94}, {"v": 75}]
 
def remove(bad, sequence, key=lambda elt : elt):
    return filter(lambda e : key(e) != bad, sequence)
 
first = lambda seq : seq[0]
rest = lambda seq : seq[1:]
 
def applicator(*funcs):
    return lambda elt : reduce(lambda res, x : x(res), rest(funcs), first(funcs)(elt))
         
r = remove(94, enumerate(a), key=applicator(itemgetter(1), itemgetter("v")))

a = [ {"v": 52}, {"v": 94}, {"v": 75} ]
for i in xrange(len(a)):
    if a[i]['v'] == 94:
        a[i]['k'] = i
    else:
        a[i] = None
print filter(None, a)