[Python] What is a good way to generate all strings of length n over a given alphabet within a...

I want to write a generator s_generator(alphabet, length, start_s, end_s) that generates strings of length n over a given alphabet in dictionary order starting with start_s and ending at end_s.

For example, s_generator('ab', 4, 'aaaa', 'bbbb') generates ['aaaa', 'aaab', 'aaba', 'aabb', 'abaa', 'abab', 'abba', 'abbb', 'baaa', 'baab', 'baba', 'babb', 'bbaa', 'bbab', 'bbba', 'bbbb']. And s_generator('ab', 4, 'abaa', 'abaa') generates ['abaa', 'abab', 'abba', 'abbb', 'baaa']

What is a good way to implement it?

I thought about assigning a number to each character in alphabet, treating the string as a base-n number (n is size of alphabet) and using addition to get the next number, and then convert the number back to string. For example, 'abab' is [0, 1, 0, 1] and the next number is [0, 1, 1, 0], which is 'abba'. This method seems complicated. Is there a simpler solution?

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