如何比较两列并获取 python pandas dataframe 中两列中所有匹配项的第三列的平均值？

Question

I have the following table named Rides :

start_id	end_id	eta
A	B	5
B	C	4
A	C	6
A	B	5
B	A	3
C	A	3
B	C	6
C	A	5
A	B	8

From the Rides Table, I want to Create a new table which should look like something like below:

start_id	end_id	mean _eta
A	B	6 ((5+5+8)/3)
B	C	5 ((4+6)/2))
A	C	6
B	A	3
C	A	4 ((3+5)/2))

so mean_eta of 1st row is returning 8 as there are three matching rides between start_ID = "A" and end_ID = "B" with eta 5,5,8 , so the mean_eta = (5+5+8)/3 = 6 How should I do it? Please help.

Answer 1

groupby and get the aggregate mean. Code below;

df.groupby(['start_id','end_id'])['eta'].agg('mean').to_frame('eta-mean')