Python合并2列表/SQL JOIN [英] Python merge 2 lists / SQL JOIN

问题描述

如果我在python中有2个列表或数据框(熊猫)，如何合并/匹配/加入它们?

If I have 2 lists or data frame (pandas) in python how do I merge / match / join them?

例如:

列表/DF 1:

Table_Name  Table_Alias
  tab_1          t1
  tab_2          t2
  tab_3          t3

列表/DF 2:

Table_Alias   Variable_Name
    t1            Owner
    t1            Owner_Id
    t2            Purchase_date
    t3            Maintenance_cost

所需结果:

Table_Name   Table_Alias   Variable_Name
   tab_1         t1            Owner
   tab_1         t1            Owner_Id
   tab_2         t2            Purchase_date
   tab_3         t3            Maintenance_cost

注意:如果我在R中执行此操作，则将使用类似以下内容的

NOTE : If I was doing this in R, I'd use something like:

df3 <- merge(df1, df2, by = 'Table_Alias', all.y = T)

在python中执行此操作的最佳方法是什么?

What's the best way to do this in python?

推荐答案

您想要外部"

You want an 'outer' merge:

In [9]:
df.merge(df1, how='outer')

Out[9]:
  Table_Name Table_Alias     Variable_Name
0      tab_1          t1             Owner
1      tab_1          t1          Owner_Id
2      tab_2          t2     Purchase_date
3      tab_3          t3  Maintenance_cost

它将在两个dfs的重叠列上进行匹配，并返回匹配行的并集.

It will match on overlapping columns from both dfs and return the union of the matching rows.

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