DRY means expressing knowledge or logic once instead of duplicating it. Repeated code is difficult to track and maintain because every copy must be found and updated when requirements change. Python functions apply DRY by packaging repeated behavior under a name, reducing duplication while enabling higher-level reasoning. section 7.0
Prefer a concise Python operation when repetition signals a better abstraction. To test whether a word begins with a vowel, replace a loop or chain of comparisons with `word[0] in 'aeiou'`; the expression is readable, short, accurate, and suitable for short strings. section 3.3
starts_with_vowel = False
for vowel in 'aeiou':
if word[0] == vowel:
starts_with_vowel = True
break
Compare the repetitive vowel-checking loop with the shorter membership test represented by `b3`; the contrast illustrates DRY as a practical code-review heuristic. section 3.3
