How to delete column if entire column values are "nan"

How to delete column if entire column values are "nan" - Printable Version

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How to delete column if entire column values are "nan" - Sri - Apr-10-2019

Hi,
I have read csv file in dataframe, and I want to delete column if entire column values are equal to "nan"

data.csv:

Name    Rank   subname prevname
USA Ca   12     23     nan
USA WD   25     78     nan
RSA      45     nan    nan

not always the entire 3rd row has "nan" values.

I use the below code:

import pandas as pd
df=pd.read_csv(r'data.csv')
 
df.dropna(axis=1, how='all')

RE: How to delete column if entire column values are "nan" - scidam - Apr-10-2019

There are at least several ways to do what you want:

# 1
df.drop('prevname', axis=1, inplace=True)

# 2
df = df.iloc[:,:-1] # we assume that prevname is a last column

# 3
df = df[['Name', 'Rank', 'subname']]

RE: How to delete column if entire column values are "nan" - Sri - Apr-11-2019

we do not know which column has nan values beforehand, and column names are not the same always.

RE: How to delete column if entire column values are "nan" - scidam - Apr-11-2019

(Apr-11-2019, 12:28 PM)Sri Wrote: we do not know which column has nan values beforehand, and column names are not the same always.

In this case, using .dropna is a good choice. You need to pass inplace=True: df.dropna(axis=1, how='all', inplace=True).

RE: How to delete column if entire column values are "nan" - Sri - Apr-13-2019

Thanks a lot!