Reputation: 1582
I am new in python and nltk. I am asked to create two different parse tree for the following sentence:
Adam slept while Josh ate and the dog barked.
Based on these two constructions:
S-> S while S
S-> S and S
Here is what I wrote so far, I used this page (4.1) as a guideline.
import nltk
grammar_string = '''
S -> S 'and' S
S -> S 'or' S
S -> S 'but' S
S -> S 'while' S
S -> S 'when' S
S -> 'Adam'|'slept'|'Josh'|'ate'|'the'|'dog'|'barked'
'''
sentence = "Adam slept while Josh ate and the dog barked"
grammar = nltk.CFG.fromstring(grammar_string)
rd_parser = nltk.RecursiveDescentParser(grammar)
sent = sentence.split()
for tree in rd_parser.parse(sent):
print(tree)
This code doesn't work. I am getting this error:
if isinstance(index, (int, slice)):
RuntimeError: maximum recursion depth exceeded in __instancecheck__
I am wondering what is wrong with my code? Is it because of this: S -> 'Adam'|'slept'|'Josh'|...
Thank you.
Upvotes: 1
Views: 130
Reputation: 12573
You probably want to define something like this (which is somewhat non-conventional, by the way):
S -> P
P -> P u P | F
F -> W | W F
u -> 'and'| 'or' | 'but' | 'while' | 'when'
W -> 'Adam'|'slept'|'Josh'|'ate'|'the'|'dog'|'barked'
'F' stays for 'fragment' here. I don't guarantee that this would generate only meaningful sentences, but it should hopefully allow the parser to terminate.
Upvotes: 1