dataframe数据自动对齐

import pandas as pd
import numpy as np

# Pandas 可以根据索引实现数据自动对齐，索引不重合的部分被置为NaN

df1 = pd.DataFrame(np.random.randint(low=1, high=10, size=(3,4)), columns=['a','b','c','d'])
df2 = pd.DataFrame(np.random.randint(low=1, high=10, size=(4,5)), columns=['a','b','c','d','e'])
df3 = pd.DataFrame(np.random.randint(low=1, high=10, size=(3,4)), columns=['e','f','g','h'])
print(df1)
print(df2)
print(df3)

print(df1 + df2)
print(df1 + df3)