There is a df_new Pandas dataframe: year date route operator group_name bus_garage district injury_result incident_type victim_category victim_sex victim_age 0 2015 01.01.2015 1 London General Go-Ahead Garage Not Available Southwark Injuries treated on scene Onboard Injuries Passenger Male Child 1 2015 01.01.2015 4 Metroline Metroline Garage Not Available Islington Injuries treated on scene Onboard Injuries Passenger Male Unknown 2 2015 01.01.2015 5 East London Stagecoach Garage Not Available Havering Taken to Hospital – Reported Serious Injury or... Onboard Injuries Passenger Male Elderly Calculate the average number of "date" string values for all "operator"

# import pandas
import pandas as pd
# read csv file
df_new = pd.read_csv('file.csv')
# calculate mean of the "date" column for each "operator"
df_new.groupby('operator')['date'].mean()