如何从pandas中的列中给定key:value对的行创建列？

df_selected = df[df['key_column'] == 'specified_key']

df['new_column'] = df_selected.apply(lambda row: row['value_column'], axis=1)

import pandas as pd

# 创建示例DataFrame
df = pd.DataFrame({'key_column': ['key1', 'key2', 'key3'],
                   'value_column': ['value1', 'value2', 'value3']})

# 使用条件筛选选择具有指定key的行
df_selected = df[df['key_column'] == 'key2']

# 使用apply函数将value值应用到新列中
df['new_column'] = df_selected.apply(lambda row: row['value_column'], axis=1)

print(df)

  key_column value_column new_column
0       key1       value1        NaN
1       key2       value2     value2
2       key3       value3        NaN