group by week in pandas

Question

I'm having this data frame:

Name   Date    Quantity Apple  07/11/17  20 orange 07/14/17  20 Apple  07/14/17  70 Orange 07/25/17  40 Apple  07/20/17  30 

I want to aggregate this by Name and Date to get sum of quantities Details:

Date: Group, the result should be at the beginning of the week (or just on Monday)

Quantity: Sum, if two or more records have same Name and Date (if falls on same interval)

The desired output is given below:

Name   Date    Quantity Apple  07/10/17  90 orange 07/10/17  20 Apple  07/17/17  30 orange 07/24/17  40 

Thanks in advance

Answer 1

First convert column date to_datetime and substract one week, as we want to sum for the week ahead of the date, not the week before that date.

Then use groupby with Grouper by W-MON and aggregate sum:

df['Date'] = pd.to_datetime(df['Date']) - pd.to_timedelta(7, unit='d') df = df.groupby(['Name', pd.Grouper(key='Date', freq='W-MON')])['Quantity']        .sum()        .reset_index()        .sort_values('Date') print (df)      Name       Date  Quantity 0   Apple 2017-07-10        90 3  orange 2017-07-10        20 1   Apple 2017-07-17        30 2  Orange 2017-07-24        40