Adding 1 to an integer value in a text file and then writing this new value on top of the old value?

Question

I am trying to get the number of golfing sessions that have been attended which exists at position position [1] in the text file and add 1 to it. I have manged to do this but now want to update the integer value. Currently the program just writes the new value on the next line instead of updating.

with open("%s.txt" % month, 'r+') as f:
  for line in f:
    lineList = line.split(",")
    if golferssName == lineList[0]:
      numSessions = int(lineList[1])
      numSessions = int(numSessions) + 1
      ineList[1] = numSessions
      f.write(str(lineList[1]))

at the moment the text file looks like this:

Tom Jones,1
2

I want the 2 to be where the 1 is :(

Answer 1

this could be another solution:

with open("%s.txt" % month, 'r') as f:
    newfilelines = []
    filelines = f.readlines()
    for fileline in filelines:
        lineList = fileline.split(",")
        if swimmersName == lineList[0]:
            lineList[1] = int(lineList[1]) + 1
            newfilelines.append(lineList[0] + ',' + str(lineList[1]) + '\n')
with open("%s.txt" % month, 'w') as f:
    for newfileline in newfilelines:
        f.write(newfileline)