合并Pandas数据帧

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
df2 = pd.DataFrame({'A': [7, 8, 9], 'B': [10, 11, 12]})

result = pd.concat([df1, df2])  # 按行连接
result = pd.concat([df1, df2], axis=1)  # 按列连接

import pandas as pd

df1 = pd.DataFrame({'key': ['A', 'B', 'C'], 'value': [1, 2, 3]})
df2 = pd.DataFrame({'key': ['B', 'C', 'D'], 'value': [4, 5, 6]})

result = pd.merge(df1, df2, on='key')  # 根据key列进行合并

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}, index=['a', 'b', 'c'])
df2 = pd.DataFrame({'C': [7, 8, 9], 'D': [10, 11, 12]}, index=['b', 'c', 'd'])

result = df1.join(df2)  # 根据索引进行合并