Question

我有像这样的pandas数据帧（df）

                         Close      Close     Close Close       Close
Date                                                                 
2000-01-03 00:00:00        NaN        NaN       NaN   NaN   -0.033944
2000-01-04 00:00:00        NaN        NaN       NaN   NaN   0.0351366
2000-01-05 00:00:00  -0.033944        NaN       NaN   NaN  -0.0172414
2000-01-06 00:00:00  0.0351366  -0.033944       NaN   NaN -0.00438596
2000-01-07 00:00:00 -0.0172414  0.0351366 -0.033944   NaN   0.0396476

在R如果我想选择第五列

five=df[,5]

且没有第5列

rest=df[,-5]

如何使用pandas dataframe进行类似的操作

我在pandas中试过这个

five=df.ix[,5]

但它给出了这个错误

 File "", line 1
    df.ix[,5]
           ^
SyntaxError: invalid syntax

Answer 1

使用iloc。它明确地是基于位置的索引器。 ix可以是两者，如果索引是基于整数的话会混淆。

df.iloc[:, [4]]

除第五栏外的其他所有

slc = list(range(df.shape[1]))
slc.remove(4)

df.iloc[:, slc]

或等效

df.iloc[:, [i for i in range(df.shape[1]) if i != 4]]

Answer 2

如果你想要第五栏：

df.ix[:,4]

将冒号粘在那里以取出该列的所有行。

要排除第五列，您可以尝试：

df.ix[:, (x for x in range(0, len(df.columns)) if x != 4)]

Answer 3

按索引选择过滤器列：

In [19]: df
Out[19]: 
                 Date     Close   Close.1   Close.2  Close.3   Close.4
0  2000-01-0300:00:00       NaN       NaN       NaN      NaN -0.033944
1  2000-01-0400:00:00       NaN       NaN       NaN      NaN  0.035137
2  2000-01-0500:00:00 -0.033944       NaN       NaN      NaN -0.017241
3  2000-01-0600:00:00  0.035137 -0.033944       NaN      NaN -0.004386
4  2000-01-0700:00:00 -0.017241  0.035137 -0.033944      NaN  0.039648

In [20]: df.ix[:, 5]
Out[20]: 
0   -0.033944
1    0.035137
2   -0.017241
3   -0.004386
4    0.039648
Name: Close.4, dtype: float64

In [21]: df.icol(5)
/usr/bin/ipython:1: FutureWarning: icol(i) is deprecated. Please use .iloc[:,i]
  #!/usr/bin/python2
Out[21]: 
0   -0.033944
1    0.035137
2   -0.017241
3   -0.004386
4    0.039648
Name: Close.4, dtype: float64

In [22]: df.iloc[:, 5]
Out[22]: 
0   -0.033944
1    0.035137
2   -0.017241
3   -0.004386
4    0.039648
Name: Close.4, dtype: float64

选择除索引以外的所有列：

In [29]: df[[df.columns[i] for i in range(len(df.columns)) if i != 5]]
Out[29]: 
                 Date     Close   Close.1   Close.2  Close.3
0  2000-01-0300:00:00       NaN       NaN       NaN      NaN
1  2000-01-0400:00:00       NaN       NaN       NaN      NaN
2  2000-01-0500:00:00 -0.033944       NaN       NaN      NaN
3  2000-01-0600:00:00  0.035137 -0.033944       NaN      NaN
4  2000-01-0700:00:00 -0.017241  0.035137 -0.033944      NaN

Answer 4

如果您的DataFrame没有列/行标签，而您想选择一些特定的列，则应使用iloc方法。

如果要选择第一列和所有行的示例：

df = dataset.iloc[:,0]

此处df变量将包含存储在数据框第一列中的值。

请记住

type(df) -> pandas.core.series.Series

希望有帮助

如何在没有列名或行名的pandas中选择列和行？

4 个答案: