Using pandas to get cumulative sum of data by days

Question

Python

I've got weather data for 122 days from Wunderground that doesn't have equal time sampling intervals. Here's a sample of my data:

Bangor Weather Data from Wunderground
Datetime,Temp(F),Precip(in.),Snow (in.),PET(in./day),Baro(mBar)
    2015-12-02 01:30:00,1.1,0.3,0.0,0.45524647117649564,1017.5 
    2015-12-02 01:53:00,1.1,0.3,0.0,0.45524647117649564,1017.6 
    2015-12-02 02:20:00,1.1,0.3,0.0,0.45524647117649564,1017.2 
    2015-12-02 02:53:00,1.7,0.5,0.0,0.500024812603692,1016.7 
    2015-12-02 02:55:00,1.7,0.3,0.0,0.500024812603692,1016.5 
    2015-12-02 03:09:00,1.1,0.3,0.0,0.45524647117649564,1016.1 
    2015-12-02 03:33:00,1.1,0.5,0.0,0.45524647117649564,1016.1 
    2015-12-02 03:53:00,1.7,0.8,0.0,0.500024812603692,1016.1 
    2015-12-02 04:34:00,1.7,0.5,0.0,0.500024812603692,1015.1 
    2015-12-02 04:46:00,1.7,0.5,0.0,0.500024812603692,1015.1 
    2015-12-02 04:53:00,1.7,0.8,0.0,0.500024812603692,1015.1 
    2015-12-02 05:13:00,1.7,0.0,0.0,0.500024812603692,1014.4 

I want to get the daily sum of snow (reset to zero for a new day) for my entire data set. I want my output would look like:

    2015-12-01,0.0
    2015-12-02,0.0
    2015-12-03,1.0
    2015-12-04,3.0
    2015-12-05,0.0
    2015-12-06,1.0

How can I use pandas to do this?

Answer 1

Is that what you want?

df.groupby(df.Datetime.dt.date)['Snow (in.)'].sum()

This will give you amount of snow (sum) per day