Sentence tokenizer fails when sentence.startswith('. ')

[zqwerty]

from nltk.tokenize import sent_tokenize
sent_tokenize('. a')

will trigger IndexError from punkt.py:_realign_boundaries. But sent_tokenize('. ') will not.

Envs:
python=3.6
nltk=3.6.6

[tomaarsen]

Thank you for the bug report!
I believe to have resolved the issue in #2922. If you are experiencing that issue, please use the develop branch instead:

pip install git+https://github.com/nltk/nltk

I'll reopen this so others can see this.

[tomaarsen]

@zqwerty
NLTK 3.6.7 has been released, which includes the fix for this issue. Thank you for reporting it! I'll close this now.