【Python】数据分析常用函数merge

在Python中，pandas库中的merge函数被广泛用于合并两个或多个DataFrame对象。merge函数的主要参数有how，on，left\_on，right\_on，left\_index，right\_index等。

1. 基本的合并

import pandas as pd
 
df1 = pd.DataFrame({'key': ['A', 'B', 'C', 'D'],
                    'value': [1, 2, 3, 5]})
 
df2 = pd.DataFrame({'key': ['B', 'D', 'D', 'E'],
                    'value': [4, 5, 6, 7]})
 
df_merged = pd.merge(df1, df2, on='key')
 
print(df_merged)

2. 使用left_on和right_on

df1 = pd.DataFrame({'lkey': ['A', 'B', 'C', 'D'],
                    'value': [1, 2, 3, 5]})
 
df2 = pd.DataFrame({'rkey': ['B', 'D', 'D', 'E'],
                    'value': [4, 5, 6, 7]})
 
df_merged = pd.merge(df1, df2, left_on='lkey', right_on='rkey')
 
print(df_merged)

3. 使用left_index和right_index

df1 = df1.set_index('key')
df2 = df2.set_index('key')
 
df_merged = pd.merge(df1, df2, left_index=True, right_index=True)
 
print(df_merged)

4. 使用how参数

df_merged = pd.merge(df1, df2, on='key', how='inner')
df_merged = pd.merge(df1, df2, on='key', how='outer')
df_merged = pd.merge(df1, df2, on='key', how='left')
df_merged = pd.merge(df1, df2, on='key', how='right')

以上就是merge函数的一些常见用法。