python之将 MultiIndex Pandas DataFrame 添加到 PyTables HDFStore 的问题

我在充满栅格的列表上使用 for 循环。在每个栅格中，我提取了一个数据数组，我想使用栅格的基本名称(日期)作为该数组的索引。为此，我使用了 Pandas DataFrame Multi-Index。然后将包含新集合索引的数组附加到 HDFStore。接下来选择具有另一个日期的光栅

代码片段:

root, ext = os.path.splitext(raster) 
name = int(decimal.Decimal(os.path.basename(root))) 
 
array = ma.MaskedArray.compressed(raster) 
arr2df = pd.DataFrame(pd.Series(data = array), columns=['rastervalue']) 
arr2df['timestamp'] = pd.Series(name,index=arr2df.index) 
arr2df.set_index('timestamp') 
store.append('rastervalue',arr2df) 

DataFrame 似乎没问题(顺便说一句，我如何检索 MultiIndex？)。

>>> arr2df 
<class 'pandas.core.frame.DataFrame'> 
  MultiIndex: 123901 entries, (0, 20060101) to (123900, 20060101) 
  Data columns (total 1 columns): 
  rastervalue    123901  non-null values 
  dtypes:        int32(1) 

但是在我检查 HDFStore 的那一刻，我的 Multi-Index 似乎消失了并变成了“values_block_1”

>>> store.root.rastervalue.table.read 
<bound method Table.read of /rastervalue/table (Table(12626172,)) '' 
  description := { 
  "index": Int64Col(shape=(), dflt=0, pos=0), 
  "values_block_0": Int32Col(shape=(1,), dflt=0, pos=1), 
  "values_block_1": Int64Col(shape=(1,), dflt=0, pos=2)} 
  byteorder := 'little' 
  chunkshape := (3276,) 
  autoIndex := True 
  colindexes := { 
    "index": Index(6, medium, shuffle, zlib(1)).is_CSI=False}> 
 
>>> store.root.rastervalue.table.read(field="values_block_1") 
array([[20060101], 
       [20060101], 
       [20060101], 
       ..., 
       [ 20060914], 
       [ 20060914], 
       [ 20060914]], dtype=int64) 

通过阅读 documentation我不知道如何在 HDFStore 中正确存储或更改 MultiIndex。有什么建议么？最后我想查询表:

 store.select('rastervalue', [ pd.Term('index', '=', '20060101')]) 

请您参考如下方法:

这是一个工作示例。

In [43]: df = DataFrame(dict(ivalue = range(123901), date = 20060101,  
              value = Series([1]*123901,dtype='int32'))).set_index(['ivalue','date']) 
 
In [44]: df 
Out[44]:  
<class 'pandas.core.frame.DataFrame'> 
MultiIndex: 123901 entries, (0, 20060101) to (123900, 20060101) 
Data columns (total 1 columns): 
value    123901  non-null values 
dtypes: int32(1) 
 
In [45]: df.head() 
Out[45]:  
                 value 
ivalue date            
0      20060101      1 
1      20060101      1 
2      20060101      1 
3      20060101      1 
4      20060101      1 
 
In [46]: store = pd.HDFStore('test.h5',mode='w') 
 
In [48]: store.append('df',df) 
 
In [49]: store 
Out[49]:  
<class 'pandas.io.pytables.HDFStore'> 
File path: test.h5 
/df            frame_table  (typ->appendable_multi,nrows->123901,ncols->3,indexers->[index],dc->[date,ivalue]) 
 
In [50]: store.get_storer('df') 
Out[50]: frame_table  (typ->appendable_multi,nrows->123901,ncols->3,indexers->[index],dc->[date,ivalue]) 
In [51]: store.get_storer('df').attrs 
Out[51]:  
/df._v_attrs (AttributeSet), 14 attributes: 
   [CLASS := 'GROUP', 
    TITLE := '', 
    VERSION := '1.0', 
    data_columns := ['date', 'ivalue'], 
    encoding := None, 
    index_cols := [(0, 'index')], 
    info := {'index': {}}, 
    levels := ['ivalue', 'date'], 
    nan_rep := 'nan', 
    non_index_axes := [(1, ['ivalue', 'date', 'value'])], 
    pandas_type := u'frame_table', 
    pandas_version := '0.10.1', 
    table_type := u'appendable_multiframe', 
    values_cols := ['values_block_0', 'date', 'ivalue']] 
 
In [52]: store.get_storer('df').table 
Out[52]:  
/df/table (Table(123901,)) '' 
  description := { 
  "index": Int64Col(shape=(), dflt=0, pos=0), 
  "values_block_0": Int32Col(shape=(1,), dflt=0, pos=1), 
  "date": Int64Col(shape=(), dflt=0, pos=2), 
  "ivalue": Int64Col(shape=(), dflt=0, pos=3)} 
  byteorder := 'little' 
  chunkshape := (2340,) 
  autoIndex := True 
  colindexes := { 
    "date": Index(6, medium, shuffle, zlib(1)).is_CSI=False, 
    "index": Index(6, medium, shuffle, zlib(1)).is_CSI=False, 
    "ivalue": Index(6, medium, shuffle, zlib(1)).is_CSI=False}