一、pd.merge()

pandas.merge(left, right, 
             how='inner', on=None, 
             left_on=None, right_on=None, 
             left_index=False, right_index=False, 
             sort=False, suffixes=('_x', '_y'), 
             copy=True, indicator=False, 
             validate=None)

left : DataFrame
right : DataFrame or named Series
how : {‘left’, ‘right’, ‘outer’, ‘inner’}, default ‘inner’（设置数据连接的集合操作规则）
- left: 返回的结果只包含左列
- right: 返回的结果只包含右列
- inner: 交集
- outer: 并集
on ：label or list（此参数只有在两个DataFrame有共同列名的时候才可以使用）
left_on与right_on: label or list, or array-like（合并两个列名不同的数据集）
left_index与right_index : bool, default False（合并索引）
suffixes : tuple of (str, str), default ('_x', '_y')（为重复列名自定义后缀）

二、pd.merge()的示例代码

# 简单连接
# 只有一个共同列名时参数 on 可省略
import pandas as pd

df1 = pd.DataFrame({'Warframe':['saryn','volt','trinity','loki'],
                   'group':['A','B','C','D']})
df2 = pd.DataFrame({'Warframe':['volt','loki','saryn','trinity'],
                   'support':[2004,2008,2012,2014]})

print(pd.merge(df1,df2))

pic1

# left_on和right_on
df3 = pd.DataFrame({'name':['saryn','volt','loki','trinity'],
                   'support':[2012,2004,2008,2014]})
print(df3)
print("===========")
print(pd.merge(df1,df3,
               left_on='Warframe',right_on='name'))

pic2

# left_index和right_index
df11 = df1.set_index('Warframe')
df22 = df2.set_index('Warframe')
print(df11)
print(df22)
print(pd.merge(df11,df22,
               left_index=True,right_index=True))

pic3

# how参数
df5 = pd.DataFrame({'name':['Ember','Frost','Garuda'],
                   'ability':['Fire','Ice','Blood']},
                  columns=['name','ability'])
df6 = pd.DataFrame({'name':['Garuda','Hydroid'],
                   'face':['beatiful','emmm']},
                  columns=['name','face'])
print(df5)
print("===================================")
print(df6)
print("===================================")
print(pd.merge(df5,df6))
print("===================================")
print(pd.merge(df5,df6,how='inner'))
print("===================================")
print(pd.merge(df5,df6,how='left'))
print("===================================")
print(pd.merge(df5,df6,how='right'))
print("===================================")
print(pd.merge(df5,df6,how='outer'))

pic4