How To Ignore Nan In Rolling Average Calculation In Python

For a time series sales forecasting task I want to create a feature that represents the average sales over the last 3 days. I have a problem when I want to predict the sales for da

Solution 1:

Here is on way adding min_periods

s=df.Sales.rolling(window=2,min_periods=1).mean()
s.iloc[0]=np.nan
s
Out[1293]: 
0      NaN
1    150.0
2    250.0
3    250.0
4    200.0
Name: Sales, dtype: float64