Pandas: Setting a value in a cell when multiple columns are empty-CodePudding

I've been looking for ways to do this natively for a little while now and can't find a solution.

I have a large dataframe where I would like to set the value in other_col to 'True' for all rows where one of a list of columns is empty.

This works for a single column page_title:

df.loc[df['page_title'].isna(), ['other_col']] = ''

But not when using a list

df.loc[df[['page_title','brand','name']].isna(), ['other_col']] = ''

Any ideas of how I could do this without using Numpy or looping through all rows? Thanks

CodePudding user response：

Maybe this is what you are looking for:

df = pd.DataFrame({
    'A' : ['1', '2', '3', np.nan], 
    'B': ['10', np.nan, np.nan, '40'], 
    'C' : ['test', 'test', 'test', 'test']})

df.loc[df[['A', 'B']].isna().any(1), ['C']] = 'value'

print(df)

Result:

     A    B      C
0    1   10   test
1    2  NaN  value
2    3  NaN  value
3  NaN   40  value

CodePudding user response：

This will allow you to set which columns you want to determine if np.nan is present and set a True/False indicator

data = {
    'Column1' : [1, 2, 3, np.nan],
    'Column2' : [1, 2, 3, 4],
    'Column3' : [1, 2, np.nan, 4]
}
df = pd.DataFrame(data)
df['other_col'] = np.where((df['Column1'].isna()) | (df['Column2'].isna()) | (df['Column3'].isna()), True, False)
df