Question

如果我想告诉pandas它应该考虑缺少负值，我会

df[df < 0] = None

但是，df[df < 0]给了我一个错误：

Traceback (most recent call last):
  File "/usr/lib/pycharm/helpers/pydev/pydevd.py", line 2411, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "/usr/lib/pycharm/helpers/pydev/pydevd.py", line 1802, in run
    launch(file, globals, locals)  # execute the script
  File "/usr/lib/pycharm/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc) 
  File "foo.py", line 47, in <module>
    df[df < 0] = None
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/frame.py", line 2296, in __setitem__
    self._setitem_frame(key, value)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/frame.py", line 2334, in _setitem_frame
    self.where(-key, value, inplace=True)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/generic.py", line 4058, in where
    transpose=self._AXIS_REVERSED)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/internals.py", line 2846, in putmask
    return self.apply('putmask', **kwargs)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/internals.py", line 2820, in apply
    copy=align_copy)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/frame.py", line 2692, in reindex_axis
    fill_value=fill_value)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/generic.py", line 2049, in reindex_axis
    {axis: [new_index, indexer]}, fill_value=fill_value, copy=copy)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/generic.py", line 2073, in _reindex_with_indexers
    copy=copy)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/internals.py", line 3503, in reindex_indexer
    self.axes[axis]._can_reindex(indexer)
  File "/usr/local/anaconda2/envs/myenv3/lib/python3.5/site-packages/pandas/core/index.py", line 2086, in _can_reindex
    raise ValueError("cannot reindex from a duplicate axis")
ValueError: cannot reindex from a duplicate axis

df.info()：

>>> df.info()
<class 'pandas.core.frame.DataFrame'>
Int64Index: 90350 entries, 0 to 90349
Columns: 177 entries, V2 to V227
dtypes: int16(1), int32(1), int8(175)
memory usage: 16.3 MB

此外，索引是唯一的：

>>> df.index.has_duplicates
Out[9]: False

以下是我的df的一些输出：发生了什么？

>>> df.head()
Out[5]: 
   V2  V4  V5  V6  V7  V8  V9  V10  V11  V23  ...   V218  V219  V220  V221  \
0  12   1   1   1  -2   1   1    2    1    8  ...      4     2     2     3   
1  12   1   2   3   4   2   2    2    2    5  ...      3     4     3     4   
2  12   1   3   2   4   2   1    2    2    4  ...      4     2     2     4   
3  12   1   1   3   4   3   1    2    1    8  ...      3     1     2     3   
4  12   1   1   1   2   1   1    1    3    8  ...      4     2     2     4   

   V222  V223  V224  V225  V226  V227  
0     4     2     4     2     3     3  
1     2     3     3     3     2     3  
2     3     1     1     2     2     3  
3     4     3     3     2     2     3  
4     3     2     3     2     3     3  

[5 rows x 177 columns]
>>> (df < 0).head()
Out[6]: 
      V2     V4     V5     V6     V7     V8     V9    V10    V11    V23  \
0  False  False  False  False   True  False  False  False  False  False   
1  False  False  False  False  False  False  False  False  False  False   
2  False  False  False  False  False  False  False  False  False  False   
3  False  False  False  False  False  False  False  False  False  False   
4  False  False  False  False  False  False  False  False  False  False   

   ...     V218   V219   V220   V221   V222   V223   V224   V225   V226   V227  
0  ...    False  False  False  False  False  False  False  False  False  False  
1  ...    False  False  False  False  False  False  False  False  False  False  
2  ...    False  False  False  False  False  False  False  False  False  False  
3  ...    False  False  False  False  False  False  False  False  False  False  
4  ...    False  False  False  False  False  False  False  False  False  False  

[5 rows x 177 columns]

错误的再现

从world values survey下载数据。我正在使用stata数据。

然后做

import pandas as pd
df = pd.read_stata('data/WV6_Stata_v_2016_01_01.dta', convert_categoricals=False)
columnIds = list(range(4, 12)) + list(range(23, 25)) + list(range(45, 55)) + \
            list(range(55, 57)) + list(range(59, 67))
columnIds += list(range(67, 70)) + list(range(82, 95)) + [95] + list(range(96, 102)) + \
             list(range(102, 125)) + list(range(127, 144))
columnIds += list(range(143, 157)) + list(range(157, 211)) + list(range(211, 215)) + \
             list(range(217, 226)) + list(range(226, 228))

columns = ['V2'] + ['V'+str(id) for id in columnIds]

df = df[columns]
df.set_index('V2', inplace=True)
df[df < 0] = None

熊猫：选择负值的字段会产生错误

错误的再现

0 个答案: