python pandas数组合并

import pandas as pd

# 创建两个DataFrame
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
df2 = pd.DataFrame({'A': [7, 8, 9], 'B': [10, 11, 12]})

# 按照行方向连接两个DataFrame
result = pd.concat([df1, df2])
print(result)

   A   B
0  1   4
1  2   5
2  3   6
0  7  10
1  8  11
2  9  12

import pandas as pd

# 创建两个DataFrame
df1 = pd.DataFrame({'key': ['A', 'B', 'C'], 'value': [1, 2, 3]})
df2 = pd.DataFrame({'key': ['B', 'C', 'D'], 'value': [4, 5, 6]})

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

  key  value_x  value_y
0   B        2        4
1   C        3        5

import pandas as pd

# 创建两个DataFrame
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}, index=[0, 1, 2])
df2 = pd.DataFrame({'C': [7, 8, 9], 'D': [10, 11, 12]}, index=[1, 2, 3])

# 根据索引进行合并
result = df1.join(df2)
print(result)

   A  B    C     D
0  1  4  NaN   NaN
1  2  5  7.0  10.0
2  3  6  8.0  11.0