python/pandas中长格式数据帧的绑定

import pandas as pd

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

# 按行连接两个数据框
result = pd.concat([df1, df2], axis=0)
print(result)

import pandas as pd

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

# 根据键'key'合并两个数据框
result = pd.merge(df1, df2, on='key')
print(result)

import pandas as pd

# 创建两个数据框
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'])

# 根据索引连接两个数据框
result = df1.join(df2)
print(result)