如何计算嵌套字典中的项目

Question

I want to collect results for each date.

For each date increment pass fail results and add date in dict if not there. Should I go with dict in dict or defaultdict?

eg dates= {'2018-03-20': [{'pass': 2}, {'fail': 3}]}

And I want to add new date if not in dates and updates 'pass'/ 'fail' value for specific date.

Answer 1

Simplest, as @Jean-FrançoisFabre points out, is to use a defaultdict of Counter objects.

The collections documentation contains detailed information on these tools.

from collections import defaultdict, Counter

d = defaultdict(Counter)

d['2018-03-20']['pass'] += 1
d['2018-03-20']['fail'] += 1
d['2018-03-20']['pass'] += 1
d['2018-04-20']['pass'] += 1
d['2018-05-20']['pass'] += 1
d['2018-04-20']['fail'] += 1

Result:

defaultdict(collections.Counter,
            {'2018-03-20': Counter({'fail': 1, 'pass': 2}),
             '2018-04-20': Counter({'fail': 1, 'pass': 1}),
             '2018-05-20': Counter({'pass': 1})})