replace string inside double quotes

[jmpatx]

I am trying to replace commas with a "^" in a string that is already quoted. Below you can see input and output. However my code does not replace the string. 

Any help would be appreciated.

Input:

Output:
Id,Category,Description,Date
1,Test,Red Cars,02/12/2017
2,Test,Blue Cars,03/01/2017
3,Test,"Green, big cars",01/05/2016

Output should be:

Output:
Id,Category,Description,Date
1,Test,Red Cars,02/12/2017
2,Test,Blue Cars,03/01/2017
3,Test,"Green^ big cars",01/05/2016

import csv

ifile = open('C:/Users/jpilon/Documents/test.csv', 'r')
reader = csv.reader(ifile,delimiter=',')
ofile = open('C:/Users/jpilon/Documents/test_new.csv', 'w')
writer = csv.writer(ofile, delimiter=',')


findlist = ['"*,*"']
replacelist = ['"*^*"']

rep = dict(zip(findlist, replacelist))

def findReplace(find, replace):
   s = ifile.read()
   s = s.replace(find, replace)
   ofile.write(s)

for item in findlist:
   findReplace(item, rep[item])

ifile.close()
ofile.close()