appending to the same csv file

[dervast]

Hi all,
inside of one of my for loops I am keeping four parameters that I want to store into four columns of a csv file

 
# part of an omitted for loop
print('to be saved to the csv, id:',id,' recordNumber: ',recordNumber, 'start_time :',start_time, 'end_time :', end_time )
print('appending to file ', savepath)

during run time what one sees in console is:

to be saved to the csv, id : [3.474377447e+09]  recordNumber:  9975 start_time : 1547445492512.0 end_time : 1547445552407.0
appending to file  69_58_68_93_31_0.csv

How I can append those values to a csv file within the for loop. The filename of course is always the same and only the new calculated four variables need to be added/appended.

Regards
Alex