Following several other posts, [e.g. Detect English verb tenses using NLTK , Identifying verb tenses in python, Python NLTK figure out tense ] I wrote the following code to dete
You can strengthen your approach in various ways. You could think more about the grammar of English and add some more rules based on whatever you observe; or you could push the statistical approach, extract some more (relevant) features and throw the whole lot at a classifier. The NLTK gives you plenty of classifiers to play with, and they're well documented in the NLTK book.
You can have the best of both worlds: Hand-written rules can be in the form of features that are fed to the classifier, which will decide when it can rely on them.