Map unique strings to integers in Python [duplicate]

Question

I have a list, let say L = ['apple','bat','apple','car','pet','bat'].

I want to convert it into Lnew = [ 1,2,1,3,4,2].

Every unique string is associated with a number.

I have a java solution using hashmap, but I don't know how to use hashmap in python. Please help.

Answer 1

x = list(set(L))
dic = dict(zip(x, list(range(1,len(x)+1))))

>>> [dic[v] for v in L]
[1, 2, 1, 3, 4, 2]

Answer 2

Here's a quick solution:

l = ['apple','bat','apple','car','pet','bat']

Create a dict that maps all unique strings to integers:

d = dict([(y,x+1) for x,y in enumerate(sorted(set(l)))])

Map each string in the original list to its respective integer:

print [d[x] for x in l]
# [1, 2, 1, 3, 4, 2]