"A solution that doesn't use integer numbers."

You can use string.ascii_lowercase. Also, try to avoid magic numbers (27).
Other than that, looks good!

Thanks! Upwoted.

Didn't know about MORSE_CODE first:)

Try this test:

def test_8():
        txt = 'ABSOLUTE\nHECK\tof a month'
        test.assert_equals(censor(txt), 'ABSOLUTE\n****\tof a month')