在 Pandas 中，如何测试给定唯一 ID 的两个数据帧中是否存在一个值？

Question

I have two dataframes like this where both frames can have multiple entries for each ID:

The first dataframe df1:

ID	Amount
101	$30
102	$300
101	$35
103	$10
104	$220
103	$370
101	$500
105	$65

The second dataframe df2 has fewer rows but the same kind of information:

ID	Amount
101	$35
102	$2
103	$25
104	$75
101	$30
102	$900

I want to compare the dataframes and find any rows that have the same Amount for a given ID in both frames. Here, for example, I want pandas to return ID 101 has having an entry for $30 in both frames. Right now my intuition is to append the dataframes like so:

df1 = df1.append(df2,ignore_index=True)
df1[df1.duplicated()]

But I wanted to know if there's a more 'pythonic' way to do this. Thanks!

Answer 1

So you want something like inner join between dataframes. You can use pd.merge

pd.merge(df1, df2, on=["ID", "Amount"])