Pandas DataFrame输出为JSON

Question

我有一个Pandas数据框，它的索引是日期时间格式，里面有一些按小时记录的数据列。我想把其中一列转换成一个JSON文件，这个文件应该是一个包含每天小时值数组的数组。

举个简单的例子：

如果我的数据框是这样的：

In [106]: 
rng = pd.date_range('1/1/2011 01:00:00', periods=12, freq='H') 
df = pd.DataFrame(randn(12, 1), index=rng, columns=['A'])

In [107]:
df

Out[107]:
                     A
2011-01-01 01:00:00 -0.067214
2011-01-01 02:00:00  0.820595
2011-01-01 03:00:00  0.442557
2011-01-01 04:00:00 -1.000434
2011-01-01 05:00:00 -0.760783
2011-01-01 06:00:00 -0.106619
2011-01-01 07:00:00  0.786618
2011-01-01 08:00:00  0.144663
2011-01-01 09:00:00 -1.455017
2011-01-01 10:00:00  0.865593
2011-01-01 11:00:00  1.289754
2011-01-01 12:00:00  0.601067

我希望得到这样的JSON文件：

[    
 [-0.0672138259,0.8205950583,0.4425568167,-1.0004337373,-0.7607833867,-0.1066187698,0.7866183048,0.1446634381,-1.4550165851,0.8655931982,1.2897541164,0.6010672247]
]

我实际的数据框有很多天，所以大概会是这样的：

[
 [value@hour1day1, value@hour2day1.....value@hour24day1],
 [value@hour1day2, value@hour2day2.....value@hour24day2],
 [value@hour1day3, value@hour2day3.....value@hour24day3],
 ....
 [value@hour1LastDay, value@hour2LastDay.....value@hour24LastDay]
]

Answer 1

import json
import pandas as pd
import numpy as np

rng = pd.date_range('1/1/2011 01:00:00', periods=12, freq='H') 
df = pd.DataFrame(np.random.randn(12, 1), index=rng, columns=['A'])

print json.dumps(df.T.as_matrix().tolist(),indent=4)

输出：

[
    [
        -0.6916923670267555, 
        0.23075256008033393, 
        1.2390943452146521, 
        -0.9421708175530891, 
        -1.4622768586461448, 
        -0.3973987276444045, 
        -0.04983495806442656, 
        -1.9139530636627042, 
        1.9562147260518052, 
        -0.8296105620697014, 
        0.2888681009437529, 
        -2.3943000262784424
    ]
]

或者作为一个完整的例子，展示多个天数，使用 groupby 功能：

rng = pd.date_range('1/1/2011 01:00:00', periods=48, freq='H') 
df = pd.DataFrame(np.random.randn(48, 1), index=rng, columns=['A'])

grouped = df.groupby(lambda x: x.day)
data = [group['A'].values.tolist() for day, group in grouped]
print json.dumps(data, indent=4)

输出：

[
    [
        -0.8939584996681688, 
        ...
        -1.1332895023662326
    ], 
    [
        -0.1514553673781838, 
        ...
        -1.8380494963443343
    ], 
    [
        -1.8342085568898159
    ]
]