Python Pandas: How to grab column of values from .agg and put into a new column? [duplicate]

Question

I'm trying to just get the sum of 'ride_value' by this groupby. How do I do that?

df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].agg(['sum'])

I'm trying to do this:

df['sum'] = df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].agg(['sum'])

But of course, that doesn't work because the right-hand side is a Pandas DataFrame.

I tried:

df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].agg(['sum'])[2]
df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].agg(['sum'])[['sum']]
df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].agg(['sum'])['sum']

Answer 1

If you want to bring back a full df input, transform

df['sum'] = df.groupby(['start_lat_3', 'start_lng_3'])['ride_value'].transform('sum')

If you want it summarised, agg

df.groupby(['start_lat_3', 'start_lng_3']).agg({'ride_value':'sum'})