使用pandas过滤数据 [英] Filtering data with pandas

问题描述

我是Pandas的新手，我想将它应用到我已经写的脚本。
我有一个csv文件，我从其中提取数据，并使用列候选人'，'最终轨道'和'状态<

I'm a newbie to Pandas and I'm trying to apply it to a script that I have already written. I have a csv file from which I extract the data, and use the columns 'candidate', 'final track' and 'status' for my data frame.

我的问题是，我想过滤数据，使用Wes Mckinney的10分钟教程中显示的方法（' http://nbviewer.ipython.org/urls/ gist.github.com/wesm/4757075/raw/a72d3450ad4924d0e74fb57c9f62d1d895ea4574/PandasTour.ipynb '）。在 In [80]中：他使用 aapl_bars.close_price ['2009-10-15'] 。

My problem is, I would like to filter the data, using perhaps the method shown in Wes Mckinney's 10min tutorial ('http://nbviewer.ipython.org/urls/gist.github.com/wesm/4757075/raw/a72d3450ad4924d0e74fb57c9f62d1d895ea4574/PandasTour.ipynb'). In the section In [80]: he uses aapl_bars.close_price['2009-10-15'].

我想使用类似的方法来选择所有具有 * 状态的数据。如果该行中没有*，则也会删除其他列中的数据。

I would like to use a similar method to select all the data which have * as a status. Data from the other columns are also deleted if there is no * in that row.

我的代码：

def establish_current_tacks(filename):

    df=pd.read_csv(filename)    
    cols=[df.iloc[:,0], df.iloc[:,10], df.iloc[:,11]]
    current_tracks=pd.concat(cols, axis=1)
    return current_tracks

我的 DataFrame ：

>>> current_tracks
<class 'pandas.core.frame.DataFrame'>
Int64Index: 707 entries, 0 to 706
Data columns (total 3 columns):
candidate       695  non-null values
 final track    670  non-null values
 status         670  non-null values
dtypes: float64(1), object(2)

想要使用 current_tracks.status ['*'] ，但不起作用

推荐答案

由于你想要过滤的数据是基于的，因此，不是数据框架索引的一部分，而是一个常规列，你需要这样做：

Since the data you want to filter based on is not part of the data frame's index, but instead is a regular column, you need to do something like this:

current_tracks[current_tracks.status == '*']

完整示例：

import pandas as pd
current_tracks = pd.DataFrame({'candidate': ['Bob', 'Jim', 'Alice'],
'final_track': [10, 15, 13], 'status': ['*', '.', '*']})
current_tracks
Out[3]: 
  candidate  final_track status
0       Bob           10      *
1       Jim           15      .
2     Alice           13      *

current_tracks[current_tracks.status == '*']
Out[4]: 
  candidate  final_track status
0       Bob           10      *
2     Alice           13      *

如果 status 是您的数据框架索引的一部分，您的原始语法将有效：

If status was part of your dataframe's index, your original syntax would have worked:

current_tracks = current_tracks.set_index('status')
current_tracks.candidate['*']
Out[8]: 
status
*           Bob
*         Alice
Name: candidate, dtype: object

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