Question

我正在使用Python 2.7，并试图通过学习指南学习Python艰难的方式。当我尝试练习49时，我遇到了问题。

Python 2.7.10 (default, Jul 14 2015, 19:46:27) 
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

>>> from ex48.parser import *
>>> x = parse_sentence([('verb', 'run'), ('direction', 'north')])
>>> x.subject
'player'
>>> x.verb
'run'
>>> x.object
'north'
>>> x = parse_sentence([('noun', 'bear'), ('verb', 'eat'), ('stop', 'the'), ('noun', 'honey')])
>>> x.subject
'bear'
>>> x.verb
'eat'
>>> x.object
'honey'

当我这样做时：

from ex48.parser import *
x = parse_sentence([('verb', 'run'), ('direction', 'north')])

Windows PowerShell为我提供了：

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'parse_sentence' is not defined

我的文件结构是：

../lexicon
     bin/
     docs/
     ex48/
         __init__.py
         lexicon.py
         parser.py
     setup.py
     tests/
         lexicon_tests.py
         __init__.py

以下是parser.py

中的代码

class ParserError(Exception):
    pass

class Sentence(object):
    def __init__(self, subject, verb, obj):
        #remember we take ('noun', 'princess') tuples and convert them
        self.subject = subject[1]
        self.verb = verb[1]
        self.object = obj[1]

    def peek(word_list):
        if word_list:
            word = word_list[0]
            return word[0]
        else:
            return None

    def match(word_list, expecting):
        if word_list:
            word = word_list.pop(0)

            if word[0] == expecting:
                return word
            else:
                return None
        else:
            return None

    def skip(word_list, word_type):
        while peek(word_list) == word_type:
            match(word_list, word_type)

    def parse_verb(word_list):
        skip(word_list, 'stop')

        if peek(word_list) == 'verb':
            return match(word_list, 'verb')
        else:
            raise ParserError("Expected a verb next")

    def parse_object(word_list):
        skip(word_list, 'stop')
        next_word = peek(word_list)

        if next_word == 'noun':
            return match(word_list, 'noun')
        elif next_word == 'direction':
            return match(word_list, 'direction')
        else:
            raise ParserError("Expected a noun or direction next.")

    def parse_subject(word_list):
        skip(word_list, 'stop')
        next_word = peek(word_list)

        if next_word == 'noun':
            return match(word_list, 'noun')
        elif next_word == 'verb':
            return ('noun', 'player')
        else:
            raise ParserError("Expected a verb next.")

    def parse_sentence(word_list):
        subj = parse_subject(word_list)
        verb = parse_verb(word_list)
        obj = parse_object(word_list)

        return Sentence(subj, verb, obj)

Answer 1

坏身份。只有部分班级的第一个功能。

class ParserError(Exception):
    pass

class Sentence(object):
    def __init__(self, subject, verb, obj):
        #remember we take ('noun', 'princess') tuples and convert them
        self.subject = subject[1]
        self.verb = verb[1]
        self.object = obj[1]

def peek(word_list):
    if word_list:
        word = word_list[0]
        return word[0]
    else:
        return None

def match(word_list, expecting):
    if word_list:
        word = word_list.pop(0)

        if word[0] == expecting:
            return word
        else:
            return None
    else:
        return None

def skip(word_list, word_type):
    while peek(word_list) == word_type:
        match(word_list, word_type)

def parse_verb(word_list):
    skip(word_list, 'stop')

    if peek(word_list) == 'verb':
        return match(word_list, 'verb')
    else:
        raise ParserError("Expected a verb next")

def parse_object(word_list):
    skip(word_list, 'stop')
    next_word = peek(word_list)

    if next_word == 'noun':
        return match(word_list, 'noun')
    elif next_word == 'direction':
        return match(word_list, 'direction')
    else:
        raise ParserError("Expected a noun or direction next.")

def parse_subject(word_list):
    skip(word_list, 'stop')
    next_word = peek(word_list)

    if next_word == 'noun':
        return match(word_list, 'noun')
    elif next_word == 'verb':
        return ('noun', 'player')
    else:
        raise ParserError("Expected a verb next.")

def parse_sentence(word_list):
    subj = parse_subject(word_list)
    verb = parse_verb(word_list)
    obj = parse_object(word_list)

    return Sentence(subj, verb, obj)

Answer 2

parse_sentence()似乎是Sentence上的一种方法。您要么取消它，以便它是文件中的顶级函数，或者将其设置为@staticmethod并将其称为Sentence.parse_sentence()。

无法导入Python类

2 个答案: