如何连接两个 pandas 列并使用该行创建一个新列？

Question

Hello I have the following pandas

A B C
l 1 4
c 2 5
d 3 6

How can I conver that on

A E T
l 1 B
c 2 B
d 3 B
l 4 C
c 5 C
d 6 C

Thanks

Answer 1

I just want to add a little to @Quang Hoang's answer to complete the solution.

df = df.melt('A')
df.rename(columns={'variable': 'T', 'value': 'E'}, inplace = True)