@属性怎么写才正确？

Question

很遗憾，我不能给你问题的情况，但我可以简单描述一下我们需要创建两个 classes:

第一个 class 创建一张试卷。老师写下科目名称、试题正确答案和成功完成的最低百分比。
二年级是学生的考试

class Testpaper:
    def __init__(self, subject, markscheme, pass_mark):
        self.subject = subject
        self.markscheme = markscheme
        self.pass_mark = pass_mark

class Student:
    def __init__(self, tests_taken = {}):
        self._tests_taken = tests_taken

    @property
    def tests_taken(self):
        if self._tests_taken == {}:
            self._tests_taken = "No tests taken"
            return self._tests_taken 
        else:
            return self._tests_taken
    
    def take_test(self, testpaper, answers):
        self._tests_taken = {}
        pass_mark = 0
        for answer in answers:
            if answer in testpaper.markscheme:
                percent = 100 / len(testpaper.markscheme)
                pass_mark += percent
        
        if pass_mark >= int(testpaper.pass_mark[:-1]):
            self._tests_taken[testpaper.subject] = f"Passed! ({round(pass_mark)}%)"
            return self._tests_taken
        else:
            self._tests_taken[testpaper.subject] = f"Failed! ({round(pass_mark)}%)"
            return self._tests_taken

这是我需要检查的内容：

paper1 = Testpaper("Maths", ["1A", "2C", "3D", "4A", "5A"], "60%")
paper2 = Testpaper("Chemistry", ["1C", "2C", "3D", "4A"], "75%")
paper3 = Testpaper("Computing", ["1D", "2C", "3C", "4B", "5D", "6C", "7A"], "75%")

student1 = Student()
student2 = Student()
paper3 = Testpaper('Computing', ['1D', '2C', '3C', '4B', '5D', '6C', '7A'], '75%')
student2 = Student()
student3 = Student()
student2.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
print(student3.tests_taken)
student3.take_test(paper1, ['1C', '2D', '3A', '4C', '5A'])
student3.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
print(student3.tests_taken)
print(paper3.subject)
print(paper3.markscheme)
print(paper3.pass_mark)

这是我的输出：

No tests taken
{'Computing': 'Failed! (43%)'}
Computing
['1D', '2C', '3C', '4B', '5D', '6C', '7A']
75%

这是正确的输出：

No tests taken
{'Maths': 'Failed! (20%)', 'Computing': 'Failed! (43%)'}
Computing
['1D', '2C', '3C', '4B', '5D', '6C', '7A']
75%

我必须改变什么？

Answer 1

删除行，重置._tests_taken变量应该更好:)

def take_test(self, testpaper, answers):
    self._tests_taken = {}        # this row resets the object._tests_taken
    pass_mark = 0

你不必重新初始化那个字典，因为在这里：

self._tests_taken[testpaper.subject] = f"Passed! ({round(pass_mark)}%)"

无论如何，您添加（如果再次使用则替换）正确的值。

也将您的属性更改为：

@property
def tests_taken(self):
    if self._tests_taken == {}:
        return "No tests taken"
    else:
        return self._tests_taken

完整代码：

class Testpaper:
    def __init__(self, subject, markscheme, pass_mark):
        self.subject = subject
        self.markscheme = markscheme
        self.pass_mark = pass_mark


class Student:
    def __init__(self, tests_taken=None):
        if tests_taken is None:
            tests_taken = {}
        self._tests_taken = tests_taken

    @property
    def tests_taken(self):
        if self._tests_taken == {}:
            return "No tests taken"
        else:
            return self._tests_taken

    def take_test(self, testpaper, answers):
        pass_mark = 0
        for answer in answers:
            if answer in testpaper.markscheme:
                percent = 100 / len(testpaper.markscheme)
                pass_mark += percent

        if pass_mark >= int(testpaper.pass_mark[:-1]):
            self._tests_taken[testpaper.subject] = f"Passed! ({round(pass_mark)}%)"
            return self._tests_taken
        else:
            self._tests_taken[testpaper.subject] = f"Failed! ({round(pass_mark)}%)"
            return self._tests_taken


if __name__ == '__main__':
    paper1 = Testpaper("Maths", ["1A", "2C", "3D", "4A", "5A"], "60%")
    paper2 = Testpaper("Chemistry", ["1C", "2C", "3D", "4A"], "75%")
    paper3 = Testpaper("Computing", ["1D", "2C", "3C", "4B", "5D", "6C", "7A"], "75%")

    student1 = Student()
    student2 = Student()
    paper3 = Testpaper('Computing', ['1D', '2C', '3C', '4B', '5D', '6C', '7A'], '75%')
    student2 = Student()
    student3 = Student()
    student2.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
    print(student3.tests_taken)
    student3.take_test(paper1, ['1C', '2D', '3A', '4C', '5A'])
    student3.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
    print(student3.tests_taken)
    print(paper3.subject)
    print(paper3.markscheme)
    print(paper3.pass_mark)

Answer 2

只需将测试更改为如下所示：

def tests_taken(self):
        if self._tests_taken == {}:
            return "No tests taken"
        else:
            return self._tests_taken

并将 __init__ 更改为如下所示：

def __init__(self, ):
        self._tests_taken = {}

完整代码是这样的：

class Testpaper:
    def __init__(self, subject, markscheme, pass_mark):
        self.subject = subject
        self.markscheme = markscheme
        self.pass_mark = pass_mark

class Student:
    def __init__(self):
        self._tests_taken = {}

    @property
    def tests_taken(self):
        if self._tests_taken == {}:
            return "No tests taken"
        else:
            return self._tests_taken
    
    def take_test(self, testpaper, answers):  
        self._tests_taken == {}
        pass_mark = 0
        for answer in answers:
            if answer in testpaper.markscheme:
                percent = 100 / len(testpaper.markscheme)
                pass_mark += percent
        
        if pass_mark >= int(testpaper.pass_mark[:-1]):
            self._tests_taken[testpaper.subject] = f"Passed! ({round(pass_mark)}%)"
        else:
            self._tests_taken[testpaper.subject] = f"Failed! ({round(pass_mark)}%)"

paper1 = Testpaper("Maths", ["1A", "2C", "3D", "4A", "5A"], "60%")
paper2 = Testpaper("Chemistry", ["1C", "2C", "3D", "4A"], "75%")
paper3 = Testpaper("Computing", ["1D", "2C", "3C", "4B", "5D", "6C", "7A"], "75%")

student1 = Student()
student2 = Student()
paper3 = Testpaper('Computing', ['1D', '2C', '3C', '4B', '5D', '6C', '7A'], '75%')
student2 = Student()
student3 = Student()
student2.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
print(student3.tests_taken)
student3.take_test(paper1, ['1C', '2D', '3A', '4C', '5A'])
student3.take_test(paper3, ['1A', '2C', '3A', '4C', '5D', '6C', '7B'])
print(student3.tests_taken)
print(paper3.subject)
print(paper3.markscheme)
print(paper3.pass_mark)

输出：

No tests taken
{'Maths': 'Failed! (20%)', 'Computing': 'Failed! (43%)'}
Computing
['1D', '2C', '3C', '4B', '5D', '6C', '7A']
75%

@属性怎么写才正确？

How to write @property correctly?

python

oop

properties