Renaming Multiple Columns in Pandas

Question

I have a one CSV files in which I want rename some of the columns with same name. my initial code looks like this

df = pd.read_csv('New.csv')

I extracted selected columns from dataframe with this code

df.columns[1::3]

this slicing gets every third columns. Now I want to rename those every third columns with same names but trying to rename my columns like this gives me an error

df.columns[1::3]= ['SomeName']
raise TypeError("Index does not support mutable operations")

Is there any way I can rename multiple columns with same name in pandas ?

Any other suggestions than doing this manually ?

If need dynamic rename, what is pattern for new column names? — jezrael, May 17 '18 at 08:19

jezrael · Accepted Answer · 2018-05-17T08:31:08.043

I think best here is use rename with unique new columns names like:

df = pd.DataFrame({'A':list('abcdef'),
                   'B':[4,5,4,5,5,4],
                   'C':[7,8,9,4,2,3],
                   'D':[1,3,5,7,1,0],
                   'E':[5,3,6,9,2,4],
                   'F':list('aaabbb')})

print (df)
   A  B  C  D  E  F
0  a  4  7  1  5  a
1  b  5  8  3  3  a
2  c  4  9  5  6  a
3  d  5  4  7  9  b
4  e  5  2  1  2  b
5  f  4  3  0  4  b

d = dict(zip(df.columns[1::3], range(len(df.columns[1::3]))))
print (d)
{'B': 0, 'E': 1}


df = df.rename(columns=d)
print (df)
   A  0  C  D  1  F
0  a  4  7  1  5  a
1  b  5  8  3  3  a
2  c  4  9  5  6  a
3  d  5  4  7  9  b
4  e  5  2  1  2  b
5  f  4  3  0  4  b

Or:

d = dict(zip(df.columns[1::3], 
             ['name{}'.format(x) for x in range(len(df.columns[1::3]))]))
print (d)
{'B': 'name0', 'E': 'name1'}

df = df.rename(columns=d)
print (df)
   A  name0  C  D  name1  F
0  a      4  7  1      5  a
1  b      5  8  3      3  a
2  c      4  9  5      6  a
3  d      5  4  7      9  b
4  e      5  2  1      2  b
5  f      4  3  0      4  b

Not recommended solution is rename for same column names:

d = dict.fromkeys(df.columns[1::3], 'Name')
print (d)
{'B': 'Name', 'E': 'Name'}

df = df.rename(columns=d)
print (df)
   A  Name  C  D  Name  F
0  a     4  7  1     5  a
1  b     5  8  3     3  a
2  c     4  9  5     6  a
3  d     5  4  7     9  b
4  e     5  2  1     2  b
5  f     4  3  0     4  b

because if want seelct column Name it return all columns in DataFrame:

print (df['Name'])
   Name  Name
0     4     5
1     5     3
2     4     6
3     5     9
4     5     2
5     4     4

The reason I want to use same column name here is that, I want to group those column names. — user96564, May 17 '18 at 09:20
like `d = dict.fromkeys(df.columns[1::3], 'Name')` and then `df['name'].sum(axis=1)` ? Then it is possible use — jezrael, May 17 '18 at 09:21
No, the target is to use that grouping columns as an index not to sum. — user96564, May 17 '18 at 09:28

Alex Roberts · Answer 2 · 2018-05-17T08:49:29.907

df.columns is of type pandas.indexes.base.Index which is why you are getting the TypeError. If you convert it to a list, then you can update (rename) using the slice, and set df.columns to that updated list.

This works for me:

lst = list(df.columns)
lst[1::3] = ['someName']*len(lst[1::3])
df.columns = lst

or to have unique new column names (as @jezrael pointed out it might not be recommended to use the same name):

lst = list(df.columns)
lst[1::3] = ['someName{}'.format(x) for x in range(len(lst[1::3]))] 
df.columns = lst

jpp · Answer 3 · 2018-05-17T09:22:28.440

1

Underlying pandas index objects are numpy arrays.

You can take advantage of this fact to slice and assign using numpy conventions.

Data from @jezrael. The need to extract values explicitly is necessitated by this known issue.

df = pd.DataFrame({'A':list('abcdef'),
                   'B':[4,5,4,5,5,4],
                   'C':[7,8,9,4,2,3],
                   'D':[1,3,5,7,1,0],
                   'E':[5,3,6,9,2,4],
                   'F':list('aaabbb')})

arr = df.columns.values
arr[1::3] = range(2)
df.columns = arr

print(df)

   A  0  C  D  1  F
0  a  4  7  1  5  a
1  b  5  8  3  3  a
2  c  4  9  5  6  a
3  d  5  4  7  9  b
4  e  5  2  1  2  b
5  f  4  3  0  4  b

edited May 17 '18 at 09:22

answered May 17 '18 at 09:13

jpp

159,742
34
281
339

No, rather not. very bad answer. https://stackoverflow.com/questions/43291781/after-rename-column-get-keyerror – jezrael May 17 '18 at 09:14
In my opinion to dangerous do it, so downvoted. But if change answer, I remove downvote, no problem. – jezrael May 17 '18 at 09:16
Just test it in `pandas 0.23.0` and still problem, so dont use it. – jezrael May 17 '18 at 09:20
In my opinion the best dont use it, because too weird behaviour. – jezrael May 17 '18 at 09:23
@jezrael, But I'm not *using it*. I'm taking a copy of the values, changing them and reassigning *back*.. this isn't the same as your linked question at all. – jpp May 17 '18 at 09:24

Renaming Multiple Columns in Pandas

3 Answers3