如何将 map 一个 dataframe 中的一列字符串值转换为另一个 dataframe 中的另一列？

Question

I have two dataframes:

Dataframe A contains the following column and values -

Column 1
A; B; C
A; D; E
B; C

Dataframe B contains the following columns and values -

Column 1	Column 2
A	Apple
B	Banana
C	Cat
D	Dog
E	Egg

Now, I want to map the values in Column 1 of Dataframe 2 to the values in Column 1 of Dataframe 1 to obtain the following column in Dataframe 1:

Column 1	Derived Column
A; B; C	Apple; Banana; Cat
A; D; E	Apple; Dog; Egg
B; C	Banana; Cat

My first thought was to iterate through each row in Dataframe 1, split the value in column 1 by ';', and then map it to Dataframe 2, but I have ~100k rows in Dataframe 1, and ~10k rows in Dataframe 2 which would make this computationally expensive. Is there a much faster way to do this? Thanks!

Answer 1

Try with series.replace with regex=True after creating a dict from the second df:

df1['Column 2'] = df1['Column 1'].replace(df2.set_index('Column 1')
                                           ['Column 2'],regex=True)

---

print(df1)

  Column 1            Column 2
0  A; B; C  Apple; Banana; Cat
1  A; D; E     Apple; Dog; Egg
2     B; C         Banana; Cat