Python 3.x Date是我的索引，需要通过填充缺失的索引序列将na值填充到索引中

这是我的数据集

RECEIPT_MONTH_YEAR   RECEIPT_MONTH
2014-01-01             1
2014-02-01             2
2014-03-01             3
2014-04-01             4
2014-05-01             5
2014-06-01             6
2014-07-01             7
2014-08-01             8
2014-09-01             9
2014-10-01             10
2014-11-01             11
2015-08-01             8
2015-09-01             9
2015-10-01             10
2015-11-01             11
2015-12-01             12

我已将“收据、月份、年份”设置为我需要填写缺失日期的索引 并在其余变量中填充na值

需要像

RECEIPT_MONTH_YEAR   RECEIPT_MONTH
2014-01-01             1
2014-02-01             2
2014-03-01             3
2014-04-01             4
2014-05-01             5
2014-06-01             6
2014-07-01             7
2014-08-01             8
2014-09-01             9
2014-10-01             10
2014-11-01             11
2014-12-01             NA
2015-01-01             NA
2015-02-01             NA
2015-03-01             NA
2015-04-01             NA
2015-05-01             NA
2015-06-01             NA
2015-07-01             NA
2015-08-01             8
2015-09-01             9
2015-10-01             10
2015-11-01             11
2015-12-01             12

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在

asfreq

df.set_index('RECEIPT_MONTH_YEAR').asfreq('MS').reset_index()
Out[62]: 
   RECEIPT_MONTH_YEAR  RECEIPT_MONTH
0          2014-01-01            1.0
1          2014-02-01            2.0
2          2014-03-01            3.0
3          2014-04-01            4.0
4          2014-05-01            5.0
5          2014-06-01            6.0
6          2014-07-01            7.0
7          2014-08-01            8.0
8          2014-09-01            9.0
9          2014-10-01           10.0
10         2014-11-01           11.0
11         2014-12-01            NaN
12         2015-01-01            NaN
13         2015-02-01            NaN
14         2015-03-01            NaN
15         2015-04-01            NaN
16         2015-05-01            NaN
17         2015-06-01            NaN
18         2015-07-01            NaN
19         2015-08-01            8.0
20         2015-09-01            9.0
21         2015-10-01           10.0
22         2015-11-01           11.0
23         2015-12-01           12.0

更新

s=df.set_index('RECEIPT_MONTH_YEAR').asfreq('MS').reset_index()
s['RECEIPT_MONTH']=s['RECEIPT_MONTH_YEAR'].dt.month

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非常感谢它的工作，但是现在我想在收据中显示月份的值。非常感谢它的工作，请看我更新的问题，我有一个变量作为净销售额，我需要用预测值填充nan值。请用想法或代码帮助我这是链接