Calculate diff two dates in hours

gistfile1.txt

import pandas as pd
df = pd.read_csv("./dates.csv")
df_length = len(df.index)
print("# Incidents: ", df_length)
df['A'] = pd.to_datetime(df["start_date"])
df['B'] = pd.to_datetime(df["end_date"])
df['MTTR'] = (df['B'] - df['A']).astype('timedelta64[h]')
print("MTTR: ", df['MTTR'].mean())