python - How do I read only some of the line using line.rstrip -

i have simple python script that's downloading dated files server. script reads log file see if file has been downloaded or not , makes decision download file or skip it.

if file not in log file (meaning has not been downloaded yet), downloads file , writes file name log. when script runs again, doesn't download file again.

how check see if file exists in log using

f = open('testfile.txt', 'r+') line in f:     if line.rstrip() == mysales + date + file:         mysalesdownload = "true"     elif line.rstrip() == myproducts + date + file:         myproductsdownload = "true"     else:         continue 

mysales + date + file - mysales_2014-05-01.txt in log file.

the problem want add delimiter (;) , downloaded date file. downloaded date tells me when script downloaded data.

 f.write( mysales + date + file + ";" + datetime.date.today() + "\n"); 

however, throws wrench reading of log file now. dates dynamic , data run on night. so, bearing in mind line this:

   mysales_2014-05-01.txt;2014-05-02  

how read semicolon don't download same file twice if script runs on night?

change line:

if line.rstrip() == mysales + date + file: 

to:

if line.rstrip()[:line.rstrip().find(';')] == mysales + date + file: 

and on.