Using Pandas to concatenate values in a column and sum corresponding values in another column

Question

For example, if i have a dataset in the first table below....

Name	Code	Thickness
CH1	3	0.5
CH1	3	0.3
CH1	4	0.4
CH1	3	0.2
CH1	5	0.6
CH1	5	0.4

.... and i want to achieve the result in the next table by grouping by the "Code" column and summing the "Thickness" column

Name	Code	Thickness	Grp_Thinckness
CH1	3	0.5	0.8
CH1	3	0.3	0.8
CH1	4	0.4	0.4
CH1	3	0.2	0.2
CH1	5	0.6	1.0
CH1	5	0.4	1.0

How do I go about this?

Answer 1

It's a gap-and-island problem. Anytime the Code changes, it creates a new island. You can solve these problems with a cumsum:

s = (df["Code"] != df["Code"].shift()).cumsum()
df["Grp_Thickness"] = df.groupby(s)["Thickness"].transform("sum")