i have a df which looks like this
a b
0 A Y
1 A N
2 A N
3 B N
4 B N
5 B N
6 B N
7 C N
8 C Y
i would like to groupby by column 'a' and column 'b' should show 'Y' whenever at least one entry is 'Y' or 'N' if ALL entries are 'N'
a b
0 A Y
1 B N
2 C Y
You are looking for max.
df.groupby('a').max().reset_index()
a b
0 A Y
1 B N
2 C Y
When doing string comparison 'Y' is greater than 'N' (i.e. 'Y' > 'N' == True), so taking the max of column b means it will be 'Y' if there is a single 'Y' in the group, otherwise 'N' will be the max value.