Вот мое решение:
dict = {'ID_recipient':[0, 1, 2, 3, 4],
'monday': [13, 10, 9, 12, 9],
'tuesday':[0, 1, 0, 1, 0],
'wednesday':[0,0,0,0,1],
'thursday':[0,0,0,0,0],
'friday':[0,0,0,0,0],
'saturday':[1,0,1,0,0],
'sunday':[0,0,0,0,0]}
df = pd.DataFrame.from_dict(dict)
df
Чтобы настроить следующий DataFrame: 
Now I create a list of all the days of week columns:
daysofweek = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday',
'saturday', 'sunday']
Now I create a new column that sums up the logical value for all days of week columns across all rows (vectorised so it's much quicker that using e.g. .iterrows() )
df['No_rows'] = (test_df[daysofweek] > 0).sum(axis=1)
This gives me the correct output as you desired:
введите описание изображения здесь
Надеюсь, это поможет!