import re
documents = ["sent1. sent2. sent3. sent4. sent5.", "sent 1. sent 2... sent 3.... sent 4. sent 5..", "sent1.sent2.sent3.sent4.sent5."]
dot_space_regex = re.compile(r'(?<=\.)\s+')
for doc in documents:
print(dot_space_regex.split(doc))
aW1wb3J0IHJlCmRvY3VtZW50cyA9IFsic2VudDEuIHNlbnQyLiBzZW50My4gc2VudDQuIHNlbnQ1LiIsICJzZW50IDEuIHNlbnQgMi4uLiBzZW50IDMuLi4uIHNlbnQgNC4gc2VudCA1Li4iLCAic2VudDEuc2VudDIuc2VudDMuc2VudDQuc2VudDUuIl0KZG90X3NwYWNlX3JlZ2V4ID0gcmUuY29tcGlsZShyJyg/PD1cLilccysnKQpmb3IgZG9jIGluIGRvY3VtZW50czoKCXByaW50KGRvdF9zcGFjZV9yZWdleC5zcGxpdChkb2MpKQoJ
['sent1.', 'sent2.', 'sent3.', 'sent4.', 'sent5.']
['sent 1.', 'sent 2...', 'sent 3....', 'sent 4.', 'sent 5..']
['sent1.sent2.sent3.sent4.sent5.']