Python - Invertir coma y punto ("," ".")

sample = 'test, otro test.'

replaces = {'.': ',', ',': '.'}

print(sample)

#metodo 1 - Iteracion

newSample = ''.join([replaces.get(s, s) for s in sample])

print(newSample)

#metodo 2 - Expr Regulares

import re

pattern = '|'.join(map(re.escape, replaces.keys()))

replace = lambda g: replaces.get(g.group())

newSample2 = re.sub(pattern, replace, sample)

print(newSample2)