I would say you have an indentation problem, at least as you wrote it here:
while not os.path.exists(file + "_" + str(i) + extension):
i+=1
print "Already 2x exists..."
print "Renaming"
shutil.copy(path, file + "_" + str(i) + extension)
should be:
while os.path.exists(file + "_" + str(i) + extension):
i+=1
print "Already 2x exists..."
print "Renaming"
shutil.copy(path, file + "_" + str(i) + extension)
Check this out, please!