Pandas: Unable to change value of a cell using while loop

Question

I am trying to use a while loop to read through all the rows of my file and edit the value of a particular cell when a condition is met.

My logic is working just fine when I am reading data from an excel. But same logic is not working when I am reading from a csv file.

Here is my logic to read from Excel file:

df = pd.read_excel('Energy Indicators.xls', 'Energy', index_col=None, na_values=['NA'], skiprows = 15, skipfooter = 38, header = 1, parse_cols ='C:F')

df = df.rename(columns = {'Unnamed: 0' : 'Country', 'Renewable Electricity Production': '% Renewable'})
df = df.drop(0, axis=0)

i = 0 
while (i !=len(df)):
    if df.iloc[i]['Country'] == "Ukraine18":
        print(df.iloc[i]['Country'])
        df.iloc[i]['Country'] = 'Ukraine'
        print(df.iloc[i]['Country'])
    i += 1
df

The result I get is:

Ukraine18
Ukraine

But when I read a CSV file:

df = pd.read_csv('world_bank.csv', skiprows = 4)
df = df.rename(columns = {'Country Name' : 'Country'})
i = 0 
while (i !=len(df)):
    if df.iloc[i]['Country'] == "Aruba":
        print(df.iloc[i]['Country'])
        df.iloc[i]['Country'] = "Arb"
        print(df.iloc[i]['Country'])
    i += 1
df

The result I get is:

Aruba
Aruba

Can someone please help? What am I doing wrong with my CSV file?

Answer 1

@Anna Iliukovich-Strakovskaia, @msr_003, you guys are right! I changed my code to df['ColumnName][i], and it worked with the CSV file. But it is not working with Excel file now.

So, it seems with data read from CSV file, df['ColumnName][i] works correctly, but with data read from Excel file, df.iloc[i]['ColumnName'] works correctly.

At time point, I have no clue why there should be a difference, because I am not working with the data 'within' the files, rather I am working on data that was read from these files into a 'dataframe'. Once the data is in the dataframe, the source shouldn't have any influence, I think.

Anyway, thank you for your help!!

Answer 2

generally i used to modify as below.

testdf = pd.read_csv("sam.csv")

testdf

   ExportIndex AgentName         Country
0            1    Prince  United Kingdom
1            2       Nit  United Kingdom
2            3     Akhil  United Kingdom
3            4     Ruiva  United Kingdom
4            5     Niraj  United Kingdom
5            6     Nitin   United States

i = 0
while(i != len(testdf)):
    if(testdf['AgentName'][i] == 'Nit'):
        testdf['AgentName'][i] = 'Nitesh'
    i += 1

testdf

   ExportIndex AgentName         Country
0            1    Prince  United Kingdom
1            2    Nitesh  United Kingdom
2            3     Akhil  United Kingdom
3            4     Ruiva  United Kingdom
4            5     Niraj  United Kingdom
5            6     Nitin   United States

But i'm not sure what's wrong with your approach.