title: Pandas and unicode
body: <p>This is a string I'm getting out of <code>pandas.DataFrame.to_json()</code>, putting it into redis, getting it out of redis elsewhere, and trying to read it via <code>pandas.read_json()</code>:</p>
  
  <pre><code>DFJ {"args":{"0":"[]","1":"[]","2":"[]","3":"[]","4":"[]","5":"[]","6":"[]","7":"[]"},"date":{"0":1385944439000000000,"1":1385944439000000000,"2":1385944440000000000,"3":1385944440000000000,"4":1385944440000000000,"5":1385944440000000000,"6":1385944440000000000,"7":1385944440000000000},"host":{"0":"yy38.segm1.org","1":"kyy1.segm1.org","2":"yy10.segm1.org","3":"yy24.segm1.org","4":"yy24.segm1.org","5":"yy34.segm1.org","6":"yy15.segm1.org","7":"yy15.segm1.org"},"kwargs":{"0":"{}","1":"{}","2":"{}","3":"{}","4":"{}","5":"{}","6":"{}","7":"{}"},"operation":{"0":"x_gbinf","1":"x_initobj","2":"x_gobjParams","3":"gtfull","4":"x_gbinf","5":"gxyzinf","6":"deletemfg","7":"gxyzinf"},"thingy":{"0":"a13yy38","1":"a19kyy1","2":"a14yy10","3":"a14yy24","4":"a14yy24","5":"a12yy34","6":"a15yy15","7":"a15yy15"},"status":{"0":-101,"1":1,"2":-101,"3":-101,"4":-101,"5":-101,"6":1,"7":-101},"time":{"0":0.000801,"1":0.003244,"2":0.002247,"3":0.002787,"4":0.001067,"5":0.002652,"6":0.004371,"7":0.000602}}
  </code></pre>
  
  <p>It seems like it does not have any unicode in it. Yet on trying to <code>.read_json()</code> it I get:</p>
  
  <pre><code>Traceback (most recent call last):
    File "./sqlprofile.py", line 160, in &lt;module&gt;
      maybe_save_dataframes(rconn, configd, results)
    File "./sqlprofile.py", line 140, in maybe_save_dataframes
      h5store.append(out_queue, df)
    File "/home/username/anaconda/lib/python2.7/site-packages/pandas/io/pytables.py", line 658, in append
      self._write_to_group(key, value, table=True, append=True, **kwargs)
    File "/home/username/anaconda/lib/python2.7/site-packages/pandas/io/pytables.py", line 923, in _write_to_group
      s.write(obj = value, append=append, complib=complib, **kwargs)
    File "/home/username/anaconda/lib/python2.7/site-packages/pandas/io/pytables.py", line 2985, in write
      **kwargs)
    File "/home/username/anaconda/lib/python2.7/site-packages/pandas/io/pytables.py", line 2717, in create_axes
      raise e
  TypeError: [unicode] is not implemented as a table column
  &gt; /home/username/anaconda/lib/python2.7/site-packages/pandas/io/pytables.py(2717)create_axes()
  -&gt; raise e
  (Pdb) locals()
  </code></pre>
  
  <p>This is what I'm getting in <code>locals()</code> - it seems that <code>append_axis</code> (column names?) values are unicode. Why?</p>
  
  <pre><code>{'append_axis': [u'args', u'date', u'host', u'kwargs', u'operation', u'thingy', u'status', u'time'], 'existing_table': None, 'blocks': [FloatBlock: [time], 1 x 8, dtype float64, ObjectBlock: [args, host, kwargs, operation, thingy], 5 x 8, dtype object, IntBlock: [status], 1 x 8, dtype int64, DatetimeBlock: [date], 1 x 8, dtype datetime64[ns]], 'axis': 1, 'self': frame_table  (typ-&gt;appendable,nrows-&gt;None,ncols-&gt;1,indexers-&gt;[index]), 'axes': [0], 'kwargs': {}, 'klass': &lt;class 'pandas.io.pytables.DataCol'&gt;, 'block_obj':   args                date            host kwargs              operation      thingy  status      time
  0   [] 2013-12-02 00:33:59  yy38.segm1.org     {}       x_gbinf  a13yy38    -101  0.000801
  1   [] 2013-12-02 00:33:59  kyy1.segm1.org     {}         x_initobj  a19kyy1       1  0.003244
  2   [] 2013-12-02 00:34:00  yy10.segm1.org     {}    x_gobjParams  a14yy10    -101  0.002247
  3   [] 2013-12-02 00:34:00  yy24.segm1.org     {}        gtfull  a14yy24    -101  0.002787
  4   [] 2013-12-02 00:34:00  yy24.segm1.org     {}       x_gbinf  a14yy24    -101  0.001067
  5   [] 2013-12-02 00:34:00  yy34.segm1.org     {}           gxyzinf  a12yy34    -101  0.002652
  6   [] 2013-12-02 00:34:00  yy15.segm1.org     {}  deletemfg  a15yy15       1  0.004371
  7   [] 2013-12-02 00:34:00  yy15.segm1.org     {}           gxyzinf  a15yy15    -101  0.000602, 'axis_labels': [u'args', u'date', u'host', u'kwargs', u'operation', u'thingy', u'status', u'time'], 'nan_rep': 'nan', 'data_columns': [], 'obj':   args                date            host kwargs              operation      thingy  status      time
  0   [] 2013-12-02 00:33:59  yy38.segm1.org     {}       x_gbinf  a13yy38    -101  0.000801
  1   [] 2013-12-02 00:33:59  kyy1.segm1.org     {}         x_initobj  a19kyy1       1  0.003244
  2   [] 2013-12-02 00:34:00  yy10.segm1.org     {}    x_gobjParams  a14yy10    -101  0.002247
  3   [] 2013-12-02 00:34:00  yy24.segm1.org     {}        gtfull  a14yy24    -101  0.002787
  4   [] 2013-12-02 00:34:00  yy24.segm1.org     {}       x_gbinf  a14yy24    -101  0.001067
  5   [] 2013-12-02 00:34:00  yy34.segm1.org     {}           gxyzinf  a12yy34    -101  0.002652
  6   [] 2013-12-02 00:34:00  yy15.segm1.org     {}  deletemfg  a15yy15       1  0.004371
  7   [] 2013-12-02 00:34:00  yy15.segm1.org     {}           gxyzinf  a15yy15    -101  0.000602, 'validate': True, 'a': (1, [u'args', u'date', u'host', u'kwargs', u'operation', u'thingy', u'status', u'time']), 'index_axes_map': {0: name-&gt;index,cname-&gt;index,axis-&gt;0,pos-&gt;0,kind-&gt;integer}, 'b': ObjectBlock: [args, host, kwargs, operation, thingy], 5 x 8, dtype object, 'e': TypeError('[unicode] is not implemented as a table column',), 'name': None, 'existing_col': None, 'j': 2, 'i': 1, 'min_itemsize': None, 'col': name-&gt;values_block_1,cname-&gt;values_block_1,dtype-&gt;None,shape-&gt;None}
  </code></pre>
  
  <p>How can I fix that? Is this a bug in Pandas / pytables?</p>
  
  <p>Environment:</p>
  
  <p>Python 2.7</p>
  
  <p>pandas==0.12.0</p>
  
  <p>tables==3.0.0</p>