days = {(0): 'Mon', (1): 'Tues', (2): 'Weds', (3): 'Thurs', (4): 'Fri', (5):
    'Sat', (6): 'Sun'}
df['day_of_week'] = df['day_of_week'].apply(lambda x: days[x])
Create a day-of-week column in a Pandas dataframe using Python