Question

如何根据python中DataFrame的列值选择列名？非常感谢，

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            Set dest = ActiveWorkbook.Sheets("Filtered Data")
            dest.Activate
            dest.Range("A2:AD1048576").Delete
            source.Activate
            source.Range("A2:AD2").AutoFilter
            Sleep 2000
            If smu = "All" Then
                source.Range("A2:AD2").AutoFilter field:=7
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            End If
    Sleep 2000
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            End If
            If market = "All" Then
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Sleep 2000
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            End If
            Sleep 2000
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            Sleep 3000
            source.Range("A3:AD" & lastraw).SpecialCells(xlCellTypeVisible).Copy
            dest.Activate
            dest.Range("A2").PasteSpecial xlPasteValues

对于每一行，检查列值，如果值<= 2，则记录列名。

对于上面的示例，输出希望为：

import pandas as pd

foo = pd.DataFrame([['A',1,2,4],['B',3,4,2],['C',5,6,1]], columns=('a', 'x', 'y','z'))
foo.set_index('a')
Out[1]:

a  x  y  z

A  1  2  4

B  3  4  2

C  5  6  1

Answer 1

使用melt，然后过滤值，然后使用assign来为值cumcount新建一个键

df=foo.melt('apple').\
        loc[lambda x : x.value<=2].\
          assign(value=lambda x : x.groupby('apple').cumcount()+1)


df.pivot('apple','value','variable')
Out[56]: 
value  1    2
apple        
A      x    y
B      z  NaN
C      z  NaN

Answer 2

这是使用mul用列标签替换值<= 2的一种方法。然后排序，将空字符串放在每一行的末尾。

import pandas as pd

foo = pd.DataFrame([['A',1,2,4],['B',3,4,2],['C',5,6,1]], columns=('apple', 'x', 'y','z'))

arr = (foo.iloc[:, 1:] <= 2).mul(foo.columns[1:].to_series(), axis=1)
arr_sorted = arr.apply(sorted, key=bool, reverse=True, axis=1).values

foo.iloc[:, 1:] = pd.DataFrame(arr_sorted.tolist(), columns=foo.columns[1:])

print(foo)

  apple  x  y z
0     A  x  y  
1     B  z     
2     C  z

熊猫-根据列值有条件地选择列名

2 个答案: