Python中如何基于两个关联字典生成箱内商品映射字典？

实现思路 #

• 初始化空字典存储最终的箱-商品对应关系
• 遍历订单到箱的映射，逐个处理每个订单
• 根据订单号从商品字典中取出对应商品列表
• 将商品列表合并到对应箱号的列表中，若箱号未在结果字典中则先初始化空列表

代码实现 #

方法1：普通字典循环实现 #

orders_to_bins = {1: 'a', 2: 'a', 3: 'b'}
items = {
    1: [49,50,51,62],
    2: [60,63,64,65],
    3: [70,71,72,74]
}

items_in_bins = {}
for order_num, bin_id in orders_to_bins.items():
    order_items = items[order_num]
    if bin_id not in items_in_bins:
        items_in_bins[bin_id] = []
    items_in_bins[bin_id].extend(order_items)

print(items_in_bins)
# 输出：{'a': [49, 50, 51, 62, 60, 63, 64, 65], 'b': [70, 71, 72, 74]}

方法2：使用collections.defaultdict简化代码 #

defaultdict会自动为不存在的键创建默认空列表，省去手动判断的步骤：

from collections import defaultdict

orders_to_bins = {1: 'a', 2: 'a', 3: 'b'}
items = {
    1: [49,50,51,62],
    2: [60,63,64,65],
    3: [70,71,72,74]
}

items_in_bins = defaultdict(list)
for order_num, bin_id in orders_to_bins.items():
    items_in_bins[bin_id].extend(items[order_num])

# 可选：将defaultdict转换为普通字典
items_in_bins = dict(items_in_bins)

print(items_in_bins)
# 输出：{'a': [49, 50, 51, 62, 60, 63, 64, 65], 'b': [70, 71, 72, 74]}

内容的提问来源于stack exchange，提问作者mars