为列表条目提供索引

Question

我有一个Python列表,如下所示:

A1 = ['a','a','a','foo','c','d','a','e','bar','bar','bar','e','d','d']

我想把它变成这个......

A2 = [1,1,1,2,3,4,1,5,6,6,6,5,4,4]

... A1中的条目按顺序排列,并在A2中给出增量索引.

有没有直接的方法在Python中执行此操作？

Answer 1

index_map = {}
result = []

i = 0 # or 1 or whatever

for value in A1:
    if value not in index_map:
        index_map[value] = i
        i = i + 1
    result.append(index_map[value])