Pandas percentage of total with groupby

Question

This is obviously simple, but as a numpy newbe I\'m getting stuck.

I have a CSV file that contains 3 columns, the State, the Office ID, and the Sales for that office

Answer 1

One-line solution:

df.join(
    df.groupby('state').agg(state_total=('sales', 'sum')),
    on='state'
).eval('sales / state_total')

This returns a Series of per-office ratios -- can be used on it's own or assigned to the original Dataframe.