Convert a list of strings to a list of integers suitable for numerical processing. Easily convert back to the strings when done.

num_to_key_mapper.py

class KeyToNumMapper(object):
    counter = 0
    mapper_key_int = {}
    mapper_int_key = {}

    def __init__(self, initial):
        map(self.add_key, initial)

    def add_key(self, key):
        if key in self.mapper_key_int:
            return self.mapper_key_int[key]
        else:
            self.mapper_key_int[key] = self.counter
            self.mapper_int_key[self.counter] = key
            self.counter += 1
            return self.counter

    def get_nums(self, keys):
        return [self.get_num(key) for key in keys]

    def get_num(self, key):
        return self.mapper_key_int[key]

    def get_key(self, num):
        return self.mapper_int_key[num]