Checking file if exist then append record

Question

I am creating a log file with line by line records.

1- If file does not exist, it should create file and append header row and the record 2- if it exists, check the text timeStamp in first line. If it exist then append the record otherwise add header columns and record itself

I tried both w,a and r+; nothing worked for me. Below is my code:

logFile = open('Dump.log', 'r+')
datalogFile = log.readline()
if 'Timestamp' in datalogFile:
    logFile.write('%s\t%s\t%s\t%s\t\n'%(timestamp,logread,logwrite,log_skipped_noweight))
    logFile.flush()
else:
    logFile.write('Timestamp\t#Read\t#Write\t#e\n')
    logFile.flush()
    logFile.write('%s\t%s\t%s\t%s\t\n'%(timestamp,logread,logwrite,log_skipped))
    logFile.flush()

Code fails if file don't exist

Answer 1

Use 'a+' mode:

logFile = open('Dump.log', 'a+')

description:

a+
Open for reading and writing. The file is created if it does not exist. The stream is positioned at the end of the file. Subsequent writes to the file will always end up at the then current end of file, irrespective of any intervening fseek(3) or similar