如何打印构造函数的属性？答案

【问题标题】：How to print attribute of constructor?如何打印构造函数的属性？
【发布时间】：2021-05-02 18:09:35
【问题描述】：

需要在构造函数Student Self.grades=[]空列表中打印列表尝试访问时会打印出地址对象

class Student:
    def __init__(self, name, year):
        self.name = name
        self.year = year
        self.grades = [] # how to print this


    def add_grade(self, grade):
        if type(grade) is Grade:
            k = self.grades
            k.append(grade)

class Grade:
    minimum_passing = 65
   
    def __init__(self, score):
        self.score = score
        


pieter = Student("pw", 10)

pieter.add_grade(Grade(100))

PS 谢谢

【问题讨论】：

标签： python python-3.x class

【解决方案1】：

如果您将项目附加到列表，那么您需要for-loop 来显示列表中所有元素的属性

for item in pieter.grades:
    print(item.score)

它会在新行中打印每个分数

pieter.add_grade(Grade(100))
pieter.add_grade(Grade(16))
pieter.add_grade(Grade(56))

for item in pieter.grades:
    print(item.score)

100
16
56

如果您使用列表推导，那么您可以将其转换为列表

scores = [ item.score for item in pieter.grades ]
print(scores)

它会显示为列表

pieter.add_grade(Grade(100))
pieter.add_grade(Grade(16))
pieter.add_grade(Grade(56))

print([ item.score for item in pieter.grades ]) 

[100, 16, 56]

你可以在 Student 中添加这个方法

 def get_scores(self):
     return [ item.score for item in self.grades ]

并用作

for item in pieter.get_scores():
    print(item)  # without .score

print(pieter.get_scores())

完整代码

class Student:
    def __init__(self, name, year):
        self.name = name
        self.year = year
        self.grades = [] # how to print this


    def add_grade(self, grade):
        if type(grade) is Grade:
            k = self.grades
            k.append(grade)

    def get_scores(self):
        return [ item.score for item in self.grades ]
    
class Grade:
    minimum_passing = 65
   
    def __init__(self, score):
        self.score = score

pieter = Student("pw", 10)

pieter.add_grade(Grade(100))
pieter.add_grade(Grade(16))
pieter.add_grade(Grade(56))

for item in pieter.grades:
    print(item.score)
    
print([ item.score for item in pieter.grades ])

for item in pieter.get_scores():
    print(item)

print(pieter.get_scores())

【讨论】：

【解决方案2】：

添加grade.score:

k.append(grade.score)

打印列表：

print(pieter.grades) # [100]

另见Python class examples。

【讨论】：