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I have my algorithm and code. It works but writes the dataframe to an entire column in my output CSV file. I want to write the dataframe to only rows where the column is equal to a certain value. This is on Line 6. Rest of logic, syntax seems fine. I researched a fair few options including sort_values(), apply(), map(), lambda, writing if statements. It seems like an easy solution but I cannot get to write the dataframe to specific rows and column combination. If this question has been asked for before, please refer me to the solution.

Thank you.

Output file - Line 1

df_Working_File = pd.read_csv('Working\WF.csv')

Input File - Line 2

df_GSTRemoved = pd.read_csv('Working\GSTRemoved.csv')

Concat for vlookup essentially in output file - Line 3

df_OriginalKey = df_GSTRemoved.apply(lambda x:x['Origin'] + x['Destination'],1)

Concat for vlookup in input file - Line 4

df_Key = df_Working_File.apply(lambda x:x['Origin'] + x['Destination'],1)

Value of column dataset to write - Line 5

df_Charge_Per_Item = df_GSTRemoved['500g']

Line 6 - I want to write the dataframe to column 9 for all rows where Origin is GL in the input file

df_Working_File.apply(df_Charge_Per_Item, df_Working_File['Origin'] == 'GL')

Line 7 - Writing to csv with no index column

df_Working_File.to_csv("Working/writetoCSV.csv", index=False)

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    Can you add sample data - 5, 6 rows with desired output? Commented May 18, 2017 at 8:15

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You can write subsets of the dataframe by using boolean vactors forexample:

# boolean vector:
selector = df_Working_File['Origin'] == 'GL'
# write only rows to csv where the vector is true:
df_Working_File[selector].to_csv("Working/writetoCSV.csv", index=False)

If you also want to write only certain columns, you can use this:

df_Working_File[selector][['col1', 'col2']].to_csv("Working/writetoCSV.csv", index=False)

Btw you can concat columns also like this:

df_OriginalKey = df_GSTRemoved.Origin + df_GSTRemoved.Destination

edit

If you want to change/edit only rows that meet certain conditions you can do this:

 selector = df_Working_File['Origin'] == 'GL'
 df_Working_File.ix[selector, 'column_to_change'] = 'changed value'

I hope this helps.

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Thank you for concat. That wrote only the rows where Origin is GL and removed all other rows where Origin is not GL. I need the other Origins to be in the file and to write to only rows where Origin is GL. # Input file Origin Destination Zone 500g GL N1 Sydney 7.563636364 GL GF Gosford 7.563636364 #Output File Format only header is provided Origin Destination Charge (per item) AAT, AAT, GL, AAT`` GL, N1` GL, GF GL, WG GL, NC GL, CB The issue is that I am not able to write to the rows where Origin is GL.

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