Replace a value in a Df based in 2 conditions-CodePudding

I am trying to replace a value in a Df based on 2 conditions and doesn´t seem to work. I have tried 2 different options: I want to replace a certain value of the column named "Debt"

Df[(Df['time_idx'] ==82) & (Df['Country'] == "France") ]["Debt"]=7

Df.iloc[0]["Debt"]=7

Any ideas of why it does not work? It doesn´t give an error but the value doesn´t change

Thanks in advance

CodePudding user response：

You're modifying a copy of the dataframe, thus the original dataframe remains unchanged.

Use loc:

Df.loc[(Df['time_idx'] ==82) & (Df['Country'] == "France"), "Debt"]=7

CodePudding user response：

example dataframe

    Name  Age
0    Tom   20
1   nick   21
2  krish   19
3   jack   18

reason why your code doesn't work is you are making changes to a sliced part as this code which returns this

df[(df['Age']==20) & (df['Name']=='Tom')]

output:

  Name  Age
0  Tom   20

and setting value using slice is not posssible and returns this warning

'''A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead'''

you can simply use .loc for accomplishing this

df.loc[((df['Age']==20) & (df['Name']=='Tom')),'Age']=9
    Name  Age
0    Tom    9
1   nick   21
2  krish   19
3   jack   18

and in your case it is

Df.loc[(Df['time_idx'] ==82) & (Df['Country'] == "France"), "Debt"]=7