pandas如何根据两个以上的列条件创建列？

Question

I have almost 10000 of rows in my data frame. I have columns Date, Time and value. I want to create a column which carries a value from value column conditional on the same Date and fixed time.

Here, I am attaching my data frames for your understanding purpose. Please note that original data comprises for more than a year for each date and 15 minutes time interval.

Any help is appreciable in advance. I want df_2 from df_1. A, B and C are the date, Time and Value columns respectively.

• List item

Answer 1

Assuming that both A and B columns are strings , the solution is quite simple. Just:

df['D'] = df.groupby([df.A + df.B.str[0:2]]).transform('first')