Pandas use variable for column names part 2

Question

Given the following data frame:

import pandas as pd
import numpy as np
df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6],
                   'C':[7,8,9],
                   'D':[1,3,5],
                   'E':[5,3,6],
                   'F':[7,4,3]})

df

    A   B   C   D   E   F
0   1   4   7   1   5   7
1   2   5   8   3   3   4
2   3   6   9   5   6   3

How can one assign column names to variables for use in referring to said column names?

For example, if I do this:

cols=['A','B']
cols2=['C','D']

I then want to do something like this:

df[cols,'F',cols2]

But the result is this:

TypeError: unhashable type: 'list'

jezrael · Accepted Answer · 2016-03-26 13:10:55Z

2

I think you need add column F to list:

allcols = cols + ['F'] + cols2
print df[allcols]
   A  B  F  C  D
0  1  4  7  7  1
1  2  5  4  8  3
2  3  6  3  9  5

Or:

print df[cols + ['F'] +cols2]
   A  B  F  C  D
0  1  4  7  7  1
1  2  5  4  8  3
2  3  6  3  9  5

answered Mar 26, 2016 at 13:10

jezrael

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Comments

Zero · Accepted Answer · 2016-03-26 13:12:04Z

1

Need give a list with columns for reference.

In [48]: df[cols+['F']+cols2]
Out[48]:
   A  B  F  C  D
0  1  4  7  7  1
1  2  5  4  8  3
2  3  6  3  9  5

and, consider using df.loc[:, cols+['F']+cols2], df.ix[:, cols+['F']+cols2] for slicing.

answered Mar 26, 2016 at 13:12

Zero

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Comments

MaxU - stand with Ukraine · Accepted Answer · 2016-03-26 13:16:07Z

1

Python 3 solution:

In [154]: df[[*cols,'F',*cols2]]
Out[154]:
   A  B  F  C  D
0  1  4  7  7  1
1  2  5  4  8  3
2  3  6  3  9  5

edited Mar 26, 2016 at 13:16

answered Mar 26, 2016 at 13:12

MaxU - stand with Ukraine

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1 Comment

jezrael Over a year ago

Maybe typo? SyntaxError: invalid syntax or maybe my python 2.7?

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