Explode rows pandas dataframe

Question

I have a pandas dataframe like the below:

Letters	Date
'Letters : a'	2021
'Letters : a,b,c'	2019
'Letters : a,b'	2017

I want to be turned into the below, using pandas/python.

Letters	Date
a	2021
a	2019
b	2019
c	2019
a	2017
b	2017

Thank you in advance

Answer 1

We can use Series.str.split to parse out the relevant information in to a list prior to using explode.

df.assign(
    Letters=df.Letters \
              .str \
              .split(" : ", expand=True)[1] \
              .str.split(",") \
         ) \
  .explode("Letters")

  Letters  Date
0       a  2021
1       a  2019
1       b  2019
1       c  2019
2       a  2017
2       b  2017

Please note the index is not reset in this answer, you can do that if you need by calling reset_index.