One python library WTF I came across recently is the autojunk parameter of the difflib SequenceMatcher class. Despite passing constructing the class with

One python library WTF I came across recently is the autojunk parameter of the difflib SequenceMatcher class. Despite passing constructing the class with difflib.SequenceMatcher(isjunk=None, ... The matcher will start classifying characters as junk once the b parameter is more than 200 characters long. So unless you read the docs carefully, your matcher will start not matching anything longer than a few characters once the input gets longer than a few sentences. The trick is to also set autojunk=False in the constructor. Its like the original writer of this component wrote the matcher for a specific application (DNA matching?) and left in the heuristic even though it isn't applicable to general use. At some point they added the autojunk parameter to gate this behaviour, but it still defaults to true, to keep backwards compat, and to confuse people. https://docs.python.org/3/library/difflib.html#difflib.SequenceMatcher https://docs.python.org/3/library/difflib.html#difflib.Seque...