python - 我正在尝试将类与 python 字典一起使用

Question

class student(object):
    def __init__(self, name, age, year):
        self.name, self.age, self.year = name, age, year
        self.grades=[]
        self.grade={}
        print(name,'-------->','Age:',age,'','Year:',year)

    def set_grades(self,score):
        self.grades.append(score)
    def get_grades(self):
        return self.grades
    def average(self):
        return sum(self.grades)/len(self.grades)
    def topgrade(self,other):
        return max(self.average(),other.average())


    def __str__(self):
        return str(self.name)+'--'+' Grades:'+str(self.grades)+'---Class average:'+str(self.average())

    def dicts(self):
        return grade[self.name]=self.grades


todd=student('Todd', 43, 4)
leah=student('Leah', 38,3)

当我运行代码时，出现错误:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\toddb\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 714, in runfile
    execfile(filename, namespace)
  File "C:\Users\toddb\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 89, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)
  File "C:/Users/toddb/Desktop/student.py", line 32
    return grade[self.name]=self.grades
                           ^
SyntaxError: invalid syntax

我尝试过多种方法来做到这一点。我是否仅限于使用列表？

Answer 1

这是因为你无法返回 Python 中的赋值结果:

class Test(object):
    pass

a = Test()
somevariable = a.attr = 10

有效 - 但一旦您想返回:

def func():
    a = Test()
    return a.testattr = 10

>>> func()
SyntaxError: invalid syntax

或者更简单:

def func():
    return a = 0

>>> func()
SyntaxError: invalid syntax

所以你需要分开分配和返回:

def dicts(self):
    grade[self.name]=self.grades
    return grade

请注意，当您尝试调用此函数时，这将引发 NameError(除非您有一个名为 grade 的全局变量)。但您可能指的是 self.grade:

def dicts(self):
    self.grade[self.name]=self.grades
    return self.grade

这反过来会永久改变您的 self.grade 字典。如果您不想这样做，可以在分配之前创建一个副本:

def dicts(self):
    grade = self.grade.copy()
    grade[self.name]=self.grades
    return grade