对列表中的项进行分组并计算总和

sales_data = [
    {'category': 'Electronics', 'amount': 1000},
    {'category': 'Clothing', 'amount': 500},
    {'category': 'Electronics', 'amount': 1500},
    {'category': 'Clothing', 'amount': 800},
    {'category': 'Books', 'amount': 300}
]

from collections import defaultdict

grouped_data = defaultdict(int)

for item in sales_data:
    grouped_data[item['category']] += item['amount']

print(dict(grouped_data))

{'Electronics': 2500, 'Clothing': 1300, 'Books': 300}

for item in sales_data:
    category = item.get('category', 'Unknown')
    grouped_data[category] += item.get('amount', 0)

for item in sales_data:
    category = item['category']
    amount = float(item['amount'])  # 确保金额是数值类型
    grouped_data[category] += amount