Question

我正在努力学习Python ex48。以下是我的代码：

class ParserError(Exception):
    pass

class Sentence(object):

    def __init__(self, subject, verb, obj):
        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)
        verbj = parse_verb(word_list)
        obj = parse_object(word_list)

        return Sentence(subj, verb, obj)

我正在尝试在终端中运行此脚本。我运行python3并首先导入脚本然后尝试运行其中一个函数。但是，我收到以下错误：

我想知道如何才能正确地从班级中获取此功能。谢谢！

Answer 1

如果你正在使用课程，你的功能会有所不同。函数定义中的第一个参数将引用对象本身，通常称为self，就像在__init__中一样。向每个其他实例方法添加self参数，然后根据需要使用其他参数（如word_list）。然后使用self.method_name参考这些实例方法。

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

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

以上只是一个示例 - 您需要以类似的方式修改其他实例方法。

无法从python中的类调用函数。学习python the hardway ex49

1 个答案: