Python / Pandas：用于循环以汇总移动范围并追加到新列

Question

I am fairly new to Python and Pandas so please forgive the uninformed question I'm posing here.

I have a dataframe (QReport) that looks like so:

DATE            STATE       SALES
2010-12-01       AL          10
2010-12-02       AL          13
2010-12-03       AL          16
2010-12-04       AL          10
2010-12-05       AL          10
2010-12-06       AL          2
2010-12-07       AL          5 
2010-12-08       AL          5

I'd like to create a seven day sales total column that sums seven day slices of sales and adds that total to a new '7DTotal' column. I've been trying to get at this through a for loop, setting x and y variables as 0 (zero) and 6 indexes which I try to increment each run through the loop:

x = 0
y = 6
for i in QReport:
    QReport['7DTotal'] = sum(QReport['SALES'][x:y])
    x = x + 1
    y = y + 1

This approach, however, is not working and is returning the same value for every row in the newly-added 7DTotal column.

Expected output would be:

DATE            STATE       SALES   7DTotal
2010-12-01       AL          10        0
2010-12-02       AL          13        0
2010-12-03       AL          16        0
2010-12-04       AL          10        0
2010-12-05       AL          10        0
2010-12-06       AL          2         0
2010-12-07       AL          5         66
2010-12-08       AL          5         61

Thanks in advance for any help!

Answer 1

You should use rolling sum:

QReport['7DTotal'] = pd.rolling_sum(QReport.SALES, 7).fillna(0)

or

# Suggested by a commenter
QReport['7DTotal'] = QReport.rolling(7).sum().fillna(0)

(The first six elements of the column will be undefined, and fillna fills them with 0s.)

Answer 2

an easy solution would be

7_day_list = []

for index in QReport.

    avg = np.mean(QReport.loc[index:index+7, 'SALES'])

    7_day_list.append(avg)

hope that helps