python - nltk.grammar.is_terminal('str') always returns true? -

python - nltk.grammar.is_terminal('str') always returns true? -

how define grammar used nltk.grammar.is_terminal() ? no matter on object cast method, true return. instead wanna have checked whether list called wordlist contains productions defined in context-free-grammar safed under grammar.cfg.

check out code on https://github.com/nltk/nltk/blob/develop/nltk/grammar.py

def is_nonterminal(item): """ :return: true if item ``nonterminal``. :rtype: bool """ homecoming isinstance(item, nonterminal) def is_terminal(item): """ homecoming true if item terminal, if hashable , not ``nonterminal``. :rtype: bool """ homecoming hasattr(item, '__hash__') , not isinstance(item, nonterminal)

although i'm not sure how functions should used, default value is_terminal() string input true.

because, firstly, strings contains __hash__ attribute, it's function hash string, see https://docs.python.org/2/reference/datamodel.html#object.hash

>>> astring = 'foo bar' >>> astring.__hash__ <method-wrapper '__hash__' of str object @ 0x7f06bb0cbcc0> >>> astring.__hash__() 8194924035431162904

secondly, string certainly not nonterminal object in nltk because class nonterminal is:

class nonterminal(object): """ non-terminal symbol context free grammar. ``nonterminal`` wrapper class node values; used ``production`` objects distinguish node values leaf values. node value wrapped ``nonterminal`` known "symbol". symbols typically strings representing phrasal categories (such ``"np"`` or ``"vp"``). however, more complex symbol types used (e.g., lexicalized grammars). since symbols node values, must immutable , hashable. 2 ``nonterminals`` considered equal if symbols equal. :see: ``cfg``, ``production`` :type _symbol: :ivar _symbol: node value corresponding ``nonterminal``. value must immutable , hashable. """

so string goes through both criteria of (1) having __hash__ attribute , (2) not nonterminal object. nltk.grammar.is_terminal() returns true strings.

then how create homecoming false, when load grammar , read nonterminal object in grammar, perchance when object created or casted nonterminal, e.g. http://www.nltk.org/_modules/nltk/parse/pchart.html

python list terminal grammar nltk