find out the value of a specific variable in python

Question

Let's say I have a data frame with 2 columns, 1st column contains the activities such as work, home, sleep etc. and the 2nd column are the duration of each activity.

while iterating through the rows, I want to find out the duration of the last activity of 'sleep' during the current activity I am in.

Is there an easy way to do that?

my data:

duration = np.random.randint(20, size = 30)
activities = ['work', 'home', 'sleep', 'home','work', 'sleep','work', 'home','sleep', 'home','work', 'sleep','work', 'home','work', 'sleep','work', 'home','work', 'sleep','work', 'home','work', 'sleep','work', 'home','work', 'home', 'work', 'sleep']
activity_df = pd.DataFrame({'activities':activities, 'duration':duration})

What is expected output?

jezrael
– jezrael

2018-06-14 10:41:28 +00:00
Commented Jun 14, 2018 at 10:41 — jezrael
– jezrael, Commented Jun 14, 2018 at 10:41

jezrael · Accepted Answer · 2018-06-14 10:47:54Z

1

I believe need first filter by boolean indexing and last select last value by iloc:

print (activity_df.loc[activity_df['activities'] == 'sleep', 'duration'].iloc[-1])

Or use where for create NaNs by condition and last forward replace values by ffill:

activity_df['new'] = activity_df['duration'].where(activity_df['activities']=='sleep').ffill()
print (activity_df)
   activities  duration   new
0        work         1   NaN
1        home         5   NaN
2       sleep        11  11.0
3        home         8  11.0
4        work        11  11.0
5       sleep         8   8.0
6        work         9   8.0
7        home        13   8.0
8       sleep        19  19.0
9        home         6  19.0
10       work        19  19.0
11      sleep        16  16.0
12       work        16  16.0
13       home         1  16.0
14       work         5  16.0
15      sleep        10  10.0
16       work         1  10.0
17       home         5  10.0
18       work         0  10.0
19      sleep         4   4.0
20       work        12   4.0
21       home         4   4.0
22       work        10   4.0
23      sleep         6   6.0
24       work        17   6.0
25       home        14   6.0
26       work         7   6.0
27       home         5   6.0
28       work        10   6.0
29      sleep         8   8.0

edited Jun 14, 2018 at 10:47

answered Jun 14, 2018 at 10:42

jezrael

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6 Comments

DonChilliConCarne Over a year ago

thank you I think I can complete my function with this

DonChilliConCarne Over a year ago

you are a god of stack overflow

jezrael Over a year ago

@MarvieDemit - I think not, there is many better coders, but maybe have no enough time to answering.

DonChilliConCarne Over a year ago

I am sure there are but this is just my personal impression, that your just seconds away answering my questions, mostly dumb but important question for me as a new python coder! I just saw that you are from Bratislava! I currently live in Vienna from the Philippines and I want to treat you some time for a beer xD

DonChilliConCarne Over a year ago

I will write you per mail throughout the day :D write you later! Thanks again!

|

Ajay Shewale · Accepted Answer · 2018-06-14 10:48:18Z

1

You can try this also, it is somewhat similar to jezrael answer.

activity_df[activity_df['activities'] == 'sleep']['duration'].iloc[-1]

answered Jun 14, 2018 at 10:48

Ajay Shewale

1591 gold badge2 silver badges13 bronze badges

2 Comments

jpp Over a year ago

Except chained indexing is explicitly discouraged in the docs. loc is clearer and less error-prone.

Ajay Shewale Over a year ago

Agreed. It is more effective to use the .loc

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