Python Rewriting Instead Of Appending

I have two csv files result.csv and sample.csv. result.csv M11251TH1230 M11543TH4292 M11435TDS144 sample.csv M11435TDS144,STB#1,Router#1 M11543TH4292,STB#2,Router#1 M11509TD99

Solution 1:

you write to the sample.csv and then you use it as input file, with the additional column. That's why you have more and more 1's and 0's in this file. Regards, Grzegorz