Evaluating multiple conditions in if-then-else block in a Pandas DataFrame

Question

I want to create a new column in a Pandas DataFrame by evaluating multiple conditions in an if-then-else block.

if events.hour <= 6:
    events[\'time_slice\         


        

Answer 1

You could create a function:

def time_slice(hour):
    if hour <= 6:
        return 'night'
    elif hour <= 12:
        return 'morning'
    elif hour <= 18:
        return 'afternoon'
    elif hour <= 23:
        return 'evening'

then events['time_slice'] = events.hour.apply(time_slice) should do the trick.

Answer 2

Here's a NumPy approach to it -

tags = ['night','morning','afternoon','evening']
events['time_slice'] = np.take(tags,((events.hour.values-1)//6).clip(min=0))

Sample run -

In [130]: events
Out[130]: 
   hour time_slice
0     0      night
1     8    morning
2    16  afternoon
3    20    evening
4     2      night
5    14  afternoon
6     7    morning
7    18  afternoon
8     8    morning
9    22    evening

Answer 3

you can use pd.cut() method in order to categorize your data:

Demo:

In [66]: events = pd.DataFrame(np.random.randint(0, 23, 10), columns=['hour'])

In [67]: events
Out[67]:
   hour
0     5
1    17
2    12
3     2
4    20
5    22
6    20
7    11
8    14
9     8

In [71]: events['time_slice'] = pd.cut(events.hour, bins=[-1, 6, 12, 18, 23], labels=['night','morning','afternoon','evening'])

In [72]: events
Out[72]:
   hour time_slice
0     5      night
1    17  afternoon
2    12    morning
3     2      night
4    20    evening
5    22    evening
6    20    evening
7    11    morning
8    14  afternoon
9     8    morning