在Pandas中，从年和周的多索引生成DateTime索引

import pandas as pd

# 创建一个多索引的DataFrame对象
data = {'value': [1, 2, 3, 4, 5]}
index = pd.MultiIndex.from_tuples([(2019, 1), (2019, 2), (2020, 1), (2020, 2), (2020, 3)], names=['year', 'week'])
df = pd.DataFrame(data, index=index)

# 将多索引的年和周转换为DateTime索引
df.index = pd.to_datetime(df.index.to_frame().assign(day=0))

# 打印结果
print(df)

            value
2019-01-01      1
2019-01-01      2
2020-01-01      3
2020-01-01      4
2020-01-01      5