Question

我想以视觉方式查看下面的结果是否是我需要的：

import nltk 
sentence = [("the", "DT"), ("little", "JJ"), ("yellow", "JJ"), ("dog", "NN"), ("barked","VBD"), ("at", "IN"), ("the", "DT"), ("cat", "NN")]

pattern = """NP: {<DT>?<JJ>*<NN>}
VBD: {<VBD>}
IN: {<IN>}"""
NPChunker = nltk.RegexpParser(pattern) 
result = NPChunker.parse(sentence)

来源：https://stackoverflow.com/a/31937278/3552975

我不解释为什么我不能对result进行漂亮的打印。

result.pretty_print()

该错误显示为TypeError: not all arguments converted during string formatting。我使用Python3.5，nltk3.3。

Answer 1

如果要查找带括号的解析输出，则可以使用Tree.pprint()：

>>> import nltk 
>>> sentence = [("the", "DT"), ("little", "JJ"), ("yellow", "JJ"), ("dog", "NN"), ("barked","VBD"), ("at", "IN"), ("the", "DT"), ("cat", "NN")]
>>> 
>>> pattern = """NP: {<DT>?<JJ>*<NN>}
... VBD: {<VBD>}
... IN: {<IN>}"""
>>> NPChunker = nltk.RegexpParser(pattern) 
>>> result = NPChunker.parse(sentence)
>>> result.pprint()
(S
  (NP the/DT little/JJ yellow/JJ dog/NN)
  (VBD barked/VBD)
  (IN at/IN)
  (NP the/DT cat/NN))

但是很可能您正在寻找

                             S                                      
            _________________|_____________________________          
           NP                        VBD       IN          NP       
   ________|_________________         |        |      _____|____     
the/DT little/JJ yellow/JJ dog/NN barked/VBD at/IN the/DT     cat/NN

让我们深入研究Tree.pretty_print() https://github.com/nltk/nltk/blob/develop/nltk/tree.py#L692中的代码：

def pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs):
    """
    Pretty-print this tree as ASCII or Unicode art.
    For explanation of the arguments, see the documentation for
    `nltk.treeprettyprinter.TreePrettyPrinter`.
    """
    from nltk.treeprettyprinter import TreePrettyPrinter
    print(TreePrettyPrinter(self, sentence, highlight).text(**kwargs),
          file=stream)

它正在创建TreePrettyPrinter对象https://github.com/nltk/nltk/blob/develop/nltk/treeprettyprinter.py#L50

class TreePrettyPrinter(object):
    def __init__(self, tree, sentence=None, highlight=()):
        if sentence is None:
            leaves = tree.leaves()
            if (leaves and not any(len(a) == 0 for a in tree.subtrees())
                    and all(isinstance(a, int) for a in leaves)):
                sentence = [str(a) for a in leaves]
            else:
                # this deals with empty nodes (frontier non-terminals)
                # and multiple/mixed terminals under non-terminals.
                tree = tree.copy(True)
                sentence = []
                for a in tree.subtrees():
                    if len(a) == 0:
                        a.append(len(sentence))
                        sentence.append(None)
                    elif any(not isinstance(b, Tree) for b in a):
                        for n, b in enumerate(a):
                            if not isinstance(b, Tree):
                                a[n] = len(sentence)
                                sentence.append('%s' % b)
        self.nodes, self.coords, self.edges, self.highlight = self.nodecoords(
                tree, sentence, highlight)

看起来出现错误的行是sentence.append('%s' % b) https://github.com/nltk/nltk/blob/develop/nltk/treeprettyprinter.py#L97

问题是为什么会引发TypeError ？

TypeError: not all arguments converted during string formatting

如果仔细看，看起来我们可以对大多数基本的python类型使用print('%s' % b)

# String
>>> x = 'abc'
>>> type(x)
<class 'str'>
>>> print('%s' % x)
abc

# Integer
>>> x = 123
>>> type(x)
<class 'int'>
>>> print('%s' % x)
123

# Float 
>>> x = 1.23
>>> type(x)
<class 'float'>
>>> print('%s' % x)
1.23

# Boolean
>>> x = True
>>> type(x)
<class 'bool'>
>>> print('%s' % x)
True

令人惊讶的是，它甚至可以在列表中使用！

>>> x = ['abc', 'def']
>>> type(x)
<class 'list'>
>>> print('%s' % x)
['abc', 'def']

但是它受tuple的阻碍！

>>> x = ('DT', 123)
>>> x = ('abc', 'def')
>>> type(x)
<class 'tuple'>
>>> print('%s' % x)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: not all arguments converted during string formatting

因此，如果我们回到https://github.com/nltk/nltk/blob/develop/nltk/treeprettyprinter.py#L95的代码

if not isinstance(b, Tree):
    a[n] = len(sentence)
    sentence.append('%s' % b)

由于我们知道sentence.append('%s' % b)无法处理tuple，因此添加元组类型检查并以某种方式将元组中的项目连接起来并转换为str会产生很好的{{ 1}}：

pretty_print

[输出]：

if not isinstance(b, Tree):
    a[n] = len(sentence)
    if type(b) == tuple:
        b = '/'.join(b)
    sentence.append('%s' % b)

让我们看看nltk即result对象的样子：

Tree

看起来叶子被保留为字符串元组列表，例如Tree('S', [Tree('NP', [('the', 'DT'), ('little', 'JJ'), ('yellow', 'JJ'), ('dog', 'NN')]), Tree('VBD', [('barked', 'VBD')]), Tree('IN', [('at', 'IN')]), Tree('NP', [('the', 'DT'), ('cat', 'NN')])])，因此我们可以进行一些修改，使其成为字符串列表，例如[('the', 'DT'), ('cat', 'NN')]，这样[('the/DT'), ('cat/NN')]会表现出色。

因为我们知道Tree.pretty_print()有助于将字符串的元组连接到所需的形式，即

Tree.pprint()

我们可以简单地输出到带括号的解析字符串，然后用(S (NP the/DT little/JJ yellow/JJ dog/NN) (VBD barked/VBD) (IN at/IN) (NP the/DT cat/NN))重新读取解析的Tree对象：

Tree.fromstring()

完成：

from nltk import Tree
Tree.fromstring(str(result)).pretty_print()

[输出]：

import nltk 
sentence = [("the", "DT"), ("little", "JJ"), ("yellow", "JJ"), ("dog", "NN"), ("barked","VBD"), ("at", "IN"), ("the", "DT"), ("cat", "NN")]

pattern = """NP: {<DT>?<JJ>*<NN>}
VBD: {<VBD>}
IN: {<IN>}"""
NPChunker = nltk.RegexpParser(pattern) 
result = NPChunker.parse(sentence)

Tree.fromstring(str(result)).pretty_print()

如何漂亮地打印nltk树对象？

1 个答案: