Python 类、实例变量和访问器方法

Question

我正在研究 Python 类(class)的问题集。我们正在被介绍给类(class)。我正在尝试 (A) 创建一个名为 Sentence 的类，该类具有单个参数字符串，并创建一个将句子存储为字符串的实例变量。 (B) 然后为该类分配访问器方法:getSentence(以字符串形式返回句子)、getWords(返回句子中的单词列表)、getLength(返回句子中的字符数)和 getNumWords(返回)句子中的单词数)。以下是我迄今为止所做的尝试:

line = "This Tuesday is Election Day"

class Sentence:
    def __init__(self, text, string, words, length, num):
        self.text = sentence
        self.string = str(self.text)
        self.words = self.text.split()
        self.length = len(self.text)
        self.num = len(self.words)

    def getSentence(self):
        return self.string

    def getWords(self):
        return self.words

    def getLength(self):
        return self.length

    def getNumWords(self):
        return self.num



line.getWords()

感谢您的宝贵时间。

下面是更新后的代码:

class Sentence:
    def __init__(self, string):
        self.astring = str(string)

    def getSentence(self):
        return self.astring

    def getWords(self):
        return (self.astring).split()

    def getLength(self):
        return len(self.astring)

    def getNumWords(self):
        return len(self.getWords())



string = Sentence("The Election is tomorrow")

print (string.getSentence())
print (string.getWords())
print (string.getLength())
print (string.getNumWords())

Answer 1

将编程视为打地鼠游戏。你必须不断地消灭这些错误。您甚至可以在编写程序之前编写一系列测试来表达类的行为方式。有多种框架可以执行此操作，包括 unittest 和 nose，但最简单的是一系列 assert 语句。他们所做的只是在表达式不为真时引发异常。

那么，让我们构建一些测试

class Sentence:
    def __init__(self, text, string, words, length, num):
        self.text = sentence
        self.string = str(self.text)
        self.words = self.text.split()
        self.length = len(self.text)
        self.num = len(self.words)

    def getSentence(self):
        return self.string

    def getWords(self):
        return self.words

    def getLength(self):
        return self.length

    def getNumWords(self):
        return self.num

line = "This Tuesday is Election Day"
assert Sentence(line), "can initialize"
assert Sentence(line).getSentence() == line, "can return sentence"
assert Sentence(line).getWords() == ['This', 'Tuesday', 'is',
    'Election', 'Day'], "can return words"
# etc...

我运行它，我得到了

Traceback (most recent call last):
  File "v.py", line 22, in <module>
    assert Sentence(line), "can initialize"
TypeError: __init__() missing 4 required positional arguments: 'string', 'words', 'length', and 'num'

哎呀，这些参数完全不需要，所以我删除它们并再次运行，我得到了

Traceback (most recent call last):
  File "v.py", line 22, in <module>
    assert Sentence(line), "can initialize"
  File "v.py", line 3, in __init__
    self.text = sentence
NameError: name 'sentence' is not defined

糟糕，参数名称不正确...继续这样做，直到一切正常。