Choices Without Side By Side Duplicates

Question

Hi! I am trying to print a list of letters (this list will never change) where duplicates are allowed but just not side by side that start with the same letter, but I need a set number of results, let's say 14 for this example. The below is what I have.

letters = ["A", "AAA", "B", "BBB", "C", "CCC", "D", "DDD", "E", "EEE"]                                                      groups = random.choices(letters, k = 14)                                                                                                print(groups)

Example return: ['B', 'CCC', 'AAA', 'A', 'EEE', 'D', 'DDD', 'B', 'B', 'A', 'C', 'E', 'AAA', 'BBB']                   Which is not great due to having 'AAA', 'A'--'D', 'DDD'---'B', 'B' next to each other.

Hope for something like this: ['B', 'CCC', 'A', 'BBB', 'EEE', 'D', 'AAA', 'B', 'E', 'B', 'CCC', 'E', 'AAA', 'BBB']    Where each string starts with a letter different than the one to the right / left of it.

Answer 1

Choose the strings one by one, and check each time if the first letter is different from the first letter of the last chosen string - if it isn't, just keep on trying other random choices.

import random

letters = ["A", "AAA", "B", "BBB", "C", "CCC", "D", "DDD", "E", "EEE"]                 

expected_length = 14
out = []
for _ in range(expected_length):
    while True:
        new = random.choice(letters)
        if not out or new[0] != out[-1][0]:
            out.append(new)
            break
print(out)
#  ['C', 'AAA', 'EEE', 'D', 'CCC', 'D', 'AAA', 'DDD', 'C', 'E', 'A', 'BBB', 'EEE', 'AAA']