Python: Renaming columns with pandas

Question

Why isn't my attempt to rename columns working? I could swear I am following the right syntax and I am not getting any errors... it's simply not doing it.

import numpy as np
import pandas as pd
header = list(range(17))
energy = pd.read_excel('Energy Indicators.xls', 
                       usecols = [2, 3, 4, 5], 
                       skiprows = list(range(17)), 
                       skipfooter = 38)

energy.rename(columns={'Unnamed: 2': 'Country', 
                       'Petajoules': 'Energy Supply', 
                       'Gigajoules': 'Energy Supply per Capita', 
                       '%': '% Renewable'})

Screenshot of my code and output in Jupyter

S.N · Accepted Answer · 2019-11-08 22:32:12Z

4

What you are missing is inplace=True to rename and apply on the original dataframe object.

Note: inplace=True returns None inplace=False returns a copy of the object with the operation performed.

import pandas as pd

df_sorted = pd.DataFrame({'duration':[1,0,2,0],'Count':[23,23,2,1]})
df_sorted.rename(columns={'duration':'NewName'},inplace=True)
print(df_sorted)

edited Nov 8, 2019 at 22:32

answered Nov 8, 2019 at 22:28

S.N

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1 Comment

alkasm Over a year ago

Alternatively, just reassign it instead of modifying it in place; it is the preferred method, as it is planned to deprecate inplace args in a (probably very distant) future pandas version.

Seananigan · Accepted Answer · 2019-11-09 00:53:43Z

3

You have two options. You can re-assign the output of energy.rename() by using energy=energy.rename() or you can add the optional argument inplace=True.

From the documentation for DataFrame.rename:

inplace : bool, default False

Whether to return a new DataFrame. If True then value of copy is ignored.

edited Nov 9, 2019 at 0:53

Seananigan

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answered Nov 8, 2019 at 22:33

AlbinoRhino

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Comments

JohanC · Accepted Answer · 2019-11-09 05:40:01Z

2

You have two options for rename

Update with the result or here directly return it because you don't modify it then

energy = energy.rename(columns={'Unnamed: 2': 'Country', 'Petajoules': 'Energy Supply', 
                                'Gigajoules': 'Energy Supply per Capita', '%' : '% Renewable'})

return energy.rename(columns={'Unnamed: 2': 'Country', 'Petajoules': 'Energy Supply', 
                              'Gigajoules': 'Energy Supply per Capita', '%' : '% Renewable'})

Change the current object

energy.rename(columns={'Unnamed: 2': 'Country', 'Petajoules': 'Energy Supply', 
                       'Gigajoules': 'Energy Supply per Capita', '%': '% Renewable'},
              inplace=True)

edited Nov 9, 2019 at 5:40

JohanC

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answered Nov 8, 2019 at 22:31

azro

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Comments

r9t · Accepted Answer · 2019-11-08 22:32:48Z

1

You dont necessarily need inplace=True. you just have to save it back to your original df

energy = energy.rename(columns={'Unnamed: 2': 'Country', 
                   'Petajoules': 'Energy Supply', 
                   'Gigajoules': 'Energy Supply per Capita', 
                   '%': '% Renewable'})

answered Nov 8, 2019 at 22:32

r9t

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