Pandas DataFrame有条件地合并

import pandas as pd

# 创建示例 DataFrame
df1 = pd.DataFrame({
    'key': ['A', 'B', 'C', 'D'],
    'value1': [1, 2, 3, 4]
})

df2 = pd.DataFrame({
    'key': ['B', 'D', 'E', 'F'],
    'value2': [5, 6, 7, 8]
})

# 内连接
inner_join_df = pd.merge(df1, df2, on='key', how='inner')
print("Inner Join:")
print(inner_join_df)

# 外连接
outer_join_df = pd.merge(df1, df2, on='key', how='outer')
print("\nOuter Join:")
print(outer_join_df)

# 左连接
left_join_df = pd.merge(df1, df2, on='key', how='left')
print("\nLeft Join:")
print(left_join_df)

# 右连接
right_join_df = pd.merge(df1, df2, on='key', how='right')
print("\nRight Join:")
print(right_join_df)

# 填充 NaN 值
filled_df = outer_join_df.fillna(0)
print("\nFilled DataFrame:")
print(filled_df)

# 重命名列
df2.rename(columns={'value2': 'value2_renamed'}, inplace=True)
merged_df = pd.merge(df1, df2, on='key', how='inner')
print("\nMerged DataFrame with Renamed Columns:")
print(merged_df)