Так, что-ли?
>>> import csv
>>> with open('ex.csv', 'w', newline='') as csvfile:
... spamwriter = csv.writer(csvfile, delimiter='.', quotechar='', quoting=csv.QUOTE_NONE)
... spamwriter.writerow(['A', 'B'])
... spamwriter.writerow(['test', 10])
$ cat ex.csv
A.B
test.10