Defensive setdefault on defaultdict

Code reviewCode quality & reviewSenior–Staff~20 min

Review this Python grouping that also tracks counts.

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1from collections import defaultdict

3def group(records):

4 groups = defaultdict(list)

5 counts = defaultdict(int)

6 for r in records:

7 groups[r.key].append(r)

8 # “defensive”: make sure the key exists in counts before incrementing

9 counts.setdefault(r.key, 0)

10 counts[r.key] = counts[r.key] + 1

11 return groups, counts

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