Find mutations of a string

find_mutations.py

from sys import argv


def has_mutation(c):
    if c == 't':
        return '7'
    if c == 'e':
        return '3'
    return None


class RWay(object):
    def __init__(self, string):
        self.root = RNode('')
        self.root.encode_string(string)

    def retrieve_strings(self):
        return self.root.retrieve_strings()


class RNode(object):
    def __init__(self, character):
        self.character = character
        self.permutation_child = None
        self.original_child = None

    def encode_string(self, string):
        # Base case: empty string
        if len(string) == 0:
            return
        c = string[0]
        perm = has_mutation(c)
        if perm is not None:
            self.permutation_child = RNode(perm)
            self.permutation_child.encode_string(string[1:])
        self.original_child = RNode(c)
        self.original_child.encode_string(string[1:])

    def retrieve_strings(self):
        """
        Retrieve the strings from this point downward

        Returns:
            List<String>
        """
        # Base case: Leaf node
        if self.original_child is None:
            return [self.character]
        base_strings = self.original_child.retrieve_strings()
        if self.permutation_child is not None:
            base_strings = base_strings + \
                self.permutation_child.retrieve_strings()
        return list(map(lambda a: self.character + a, base_strings))


if __name__ == '__main__':
    rway = RWay(argv[1])
    print(rway.retrieve_strings())