Python: Rename duplicates in list with progressive numbers without sorting list

Question

Given a list like this:

mylist = [\"name\", \"state\", \"name\", \"city\", \"name\", \"zip\", \"zip\"]

I would like to rename the duplicate

Answer 1

Any method where count is called on each element is going to result in O(n^2) since count is O(n). You can do something like this:

# not modifying original list
from collections import Counter

mylist = ["name", "state", "name", "city", "name", "zip", "zip"]
counts = {k:v for k,v in Counter(mylist).items() if v > 1}
newlist = mylist[:]

for i in reversed(range(len(mylist))):
    item = mylist[i]
    if item in counts and counts[item]:
        newlist[i] += str(counts[item])
        counts[item]-=1
print(newlist)

# ['name1', 'state', 'name2', 'city', 'name3', 'zip1', 'zip2']

---

# modifying original list
from collections import Counter

mylist = ["name", "state", "name", "city", "name", "zip", "zip"]
counts = {k:v for k,v in Counter(mylist).items() if v > 1}      

for i in reversed(range(len(mylist))):
    item = mylist[i]
    if item in counts and counts[item]:
        mylist[i] += str(counts[item])
        counts[item]-=1
print(mylist)

# ['name1', 'state', 'name2', 'city', 'name3', 'zip1', 'zip2']

This should be O(n).

Other provided answers:

mylist.index(s) per element causes O(n^2)

mylist = ["name", "state", "name", "city", "name", "zip", "zip"]

from collections import Counter
counts = Counter(mylist)
for s,num in counts.items():
    if num > 1:
        for suffix in range(1, num + 1):
            mylist[mylist.index(s)] = s + str(suffix) 

---

count(x[1]) per element causes O(n^2)
It is also used multiple times per element along with list slicing.

print map(lambda x: x[1] + str(mylist[:x[0]].count(x[1]) + 1) if mylist.count(x[1]) > 1 else x[1], enumerate(mylist))

Benchmarks:

http://nbviewer.ipython.org/gist/dting/c28fb161de7b6287491b