catyre's code

from random import sample

alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
stream = []
prev_chars = ["", "", ""]
for _ in range(10):
    chars = sample(alphabet, 3)

    for boolean in (c1 == c2 for c1, c2 in zip(chars, prev_chars)):
        if boolean:
            print(f"Repeated letters {(chars, prev_chars)}.  Resampling...")
            #chars = sample(alphabet, 3)
            break

    prev_chars = chars
    stream.append(chars)
print(stream)