如何在 pandas dataframe 中创建新日期并作为索引插入？

Question

Im predicting total sales for next month and set the date as index in dataframe. How do I calculate new upcoming month as index and put it in a new row in the same dataframe?

I use this code below to get a new date from previous date:

from datetime import timedelta

last_date = df.iloc[[-1]].index
last_date = last_date + timedelta(days=30)

df= df.append(pd.DataFrame(index=[last_date]))

df.tail()

But, the output seemed not correct. Im expecting the result will be like below for the new upcoming index:

2017-07-30

But, instead, the output is like this:

(2017-07-30 00:00:00,)

How can I remove the time and also the unnecessary symbol there?

Answer 1

You are close, remove [] for avoid MultiIndex :

df = df.append(pd.DataFrame(index=last_date))

Sample :

from datetime import timedelta

rng = pd.date_range('2017-04-03', periods=3)
df = pd.DataFrame({'a': range(3)}, index=rng)  

last_date = df.iloc[[-1]].index
last_date = last_date + timedelta(days=30)


df = df.append(pd.DataFrame(index=last_date))
print (df)
              a
2017-04-03  0.0
2017-04-04  1.0
2017-04-05  2.0
2017-05-05  NaN

---

Test index of DataFrame with [] :

df = pd.DataFrame(index=[last_date])
print (df.index)
MultiIndex([('2017-05-05',)],
           )