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python - 在熊猫python中获取数据框的一列时出错

问题描述

我有这个简单的代码：

import pathlib
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns

wdataset =pd.read_csv('C:\MyData\sampleData.csv', header=None)
print(wdataset.tail(3))
print(wdataset[0])

当我运行此代码时，我收到此错误：

Traceback (most recent call last):
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\indexes\base.py", line 3078, in get_loc
    return self._engine.get_loc(key)
  File "pandas\_libs\index.pyx", line 140, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 162, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 1492, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 1500, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 0

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\Users\j\.vscode\extensions\ms-python.python-2019.8.29288\pythonFiles\ptvsd_launcher.py", line 43, in <module>
    main(ptvsdArgs)
  File "c:\Users\j\.vscode\extensions\ms-python.python-2019.8.29288\pythonFiles\lib\python\ptvsd\__main__.py", line 432, in main
    run()
  File "c:\Users\j\.vscode\extensions\ms-python.python-2019.8.29288\pythonFiles\lib\python\ptvsd\__main__.py", line 316, in run_file
    runpy.run_path(target, run_name='__main__')
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "c:\MyData\RCSV.py", line 12, in <module>
    print(wdataset[0])
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\frame.py", line 2688, in __getitem__
    return self._getitem_column(key)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\frame.py", line 2695, in _getitem_column
    return self._get_item_cache(key)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\generic.py", line 2489, in _get_item_cache
    values = self._data.get(item)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\internals.py", line 4115, in get
    loc = self.items.get_loc(item)
  File "C:\Users\j\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\indexes\base.py", line 3080, in get_loc
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas\_libs\index.pyx", line 140, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 162, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 1492, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 1500, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 0

有什么问题，我该如何解决？

标签： pythonpandasdataframe

解决方案

您可以使用 iloc 或 loc 命令。使用 iloc，您可以指定数字，而使用 loc 您可以指定名称。例如

data.iloc[:,0] # to get all rows of zeroth column
#For more than one column
data.iloc[:,0:3]


data.loc[:,['zeroth column name']] # get all rows of zeroth column
#For more than one column

data.loc[:,['first column name','second column name']]

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