python3-cookbook/cookbook/c01/p15_group.py

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
"""
Topic: 分组迭代
Desc : 
"""
from operator import itemgetter
from itertools import groupby


def group_iter():
    rows = [
        {'address': '5412 N CLARK', 'date': '07/01/2012'},
        {'address': '5148 N CLARK', 'date': '07/04/2012'},
        {'address': '5800 E 58TH', 'date': '07/02/2012'},
        {'address': '2122 N CLARK', 'date': '07/03/2012'},
        {'address': '5645 N RAVENSWOOD', 'date': '07/02/2012'},
        {'address': '1060 W ADDISON', 'date': '07/02/2012'},
        {'address': '4801 N BROADWAY', 'date': '07/01/2012'},
        {'address': '1039 W GRANVILLE', 'date': '07/04/2012'},
    ]

    # Sort by the desired field first
    rows.sort(key=itemgetter('date'))
    # Iterate in groups
    for date, items in groupby(rows, key=itemgetter('date')):
        print(date)
        for i in items:
            print(' ', i)

    # defaultdict使用
    from collections import defaultdict
    rows_by_date = defaultdict(list)
    for row in rows:
        rows_by_date[row['date']].append(row)

if __name__ == '__main__':
    group_iter()