cfg.py 文件源码

def demo():
    from nltk import Nonterminal, CFG
    nonterminals = 'S VP NP PP P N Name V Det'
    (S, VP, NP, PP, P, N, Name, V, Det) = [Nonterminal(s)
                                           for s in nonterminals.split()]

    grammar = CFG.fromstring("""
    S -> NP VP
    PP -> P NP
    NP -> Det N
    NP -> NP PP
    VP -> V NP
    VP -> VP PP
    Det -> 'a'
    Det -> 'the'
    Det -> 'my'
    NP -> 'I'
    N -> 'dog'
    N -> 'man'
    N -> 'park'
    N -> 'statue'
    V -> 'saw'
    P -> 'in'
    P -> 'up'
    P -> 'over'
    P -> 'with'
    """)

    def cb(grammar): print(grammar)
    top = Tk()
    editor = CFGEditor(top, grammar, cb)
    Label(top, text='\nTesting CFG Editor\n').pack()
    Button(top, text='Quit', command=top.destroy).pack()
    top.mainloop()