熊猫：写数据帧到JSON

Question

我有数据帧：

  date id 
0 12-12-2015 123 
1 13-12-2015 123 
2 15-12-2015 123 
3 16-12-2015 123 
4 18-12-2015 123 
5 12-12-2015 456 
6 13-12-2015 456 
7 15-12-2015 456 

我需要统计date到id 我尝试df.groupby('id')['date'].count() 我需要（如日期不在ID，它等于0）

 id date count 
0 123 12-12-2015 1 
1 123 13-12-2015 1 
2 123 14-12-2015 0 
3 123 15-12-2015 1 
4 123 16-12-2015 1 
5 123 17-12-2015 0 
6 123 18-12-2015 1 
7 456 12-12-2015 1 
8 456 13-12-2015 1 
9 456 14-12-2015 0 
10 456 15-12-2015 1 

而且它旁边写json文件格式

{ 
"1234567890abcdef1234567890abcdef": { 
    "2016-06": 1, 
    "2016-05": 0, 
    "2016-04": 0, 
    "2016-03": 1, 
    "2016-02": 1, 
    "2016-01": 0 
}, 
"0987654321abcdef1234567890abcdef": { 
    "2016-06": 1, 
    "2016-05": 1, 
    "2016-04": 1, 
    "2016-03": 0, 
    "2016-02": 0, 
    "2016-01": 0 
} 

}

我该怎么做？

Answer 1

首先使用resample：

df['date'] = pd.to_datetime(df.date) 
df.set_index('date', inplace=True) 

df = df.groupby('id').resample('D').size().reset_index(name='val') 
print (df) 

    id  date val 
0 123 2015-12-12 1 
1 123 2015-12-13 1 
2 123 2015-12-14 0 
3 123 2015-12-15 1 
4 123 2015-12-16 1 
5 123 2015-12-17 0 
6 123 2015-12-18 1 
7 456 2015-12-12 1 
8 456 2015-12-13 1 
9 456 2015-12-14 0 
10 456 2015-12-15 1 

然后to_json：

#remove 00:00:00 from datetime 
df['date'] = df.date.dt.date 
print (df.groupby('id').apply(lambda x: x.set_index('date')['val'].to_dict()).to_json()) 

{"123":{"2015-12-18":1,"2015-12-15":1,"2015-12-12":1,"2015-12-16":1,"2015-12-13":1,"2015-12-17":0,"2015-12-14":0}, 
"456":{"2015-12-15":1,"2015-12-12":1,"2015-12-13":1,"2015-12-14":0}}