print and sort a list of class in oop python-CodePudding

I have a class name Student like this:

class Student:
    def __init__(self, name = '', age = 0, test_score = 0):
        self.name = name
        self.age = age
        self.test_Scores = test_score
    def __str__(self):
        return "({0},{1},{2})".format(self.name,self.age, self.test_Scores)

and class name Students:

class Students():
    stds = list()
    def __init__(self) -> None:
        pass
    def Input(self):
        while True:
            inputName = input('Enter name: ')
            inputAge = int(input('Enter age: '))
            inputTestScore = int(input('Enter test score: '))
            std = Student(inputName, inputAge, inputTestScore)
            if inputAge == 0:
                break
            self.stds.append(std)
    def __str__(self):
        return str(self.stds)

Here are some code print out a list of students:

stds = Students()
stds.Input()
print(stds)

With 2 elements in the list, the result after excute look like this: [<main.Student object at 0x0000026EDEBC5FA0>, <main.Student object at 0x0000026EDEBC5CD0>]

I can't print out stds under a string, how can i fix it. And how to sort stds by the decreasing of age ? Pls help me !

CodePudding user response：

You shouldn't have class Students, you should have a list of Student. To get the data from the class variables override the __repr__ method. To sort the list you can use lambda with the attribute to sort by as key in sort() function

class Student:
    def __init__(self, name='', age=0, test_score=0):
        self.name = name
        self.age = age
        self.test_Scores = test_score

    def __repr__(self):
        return "({0},{1},{2})".format(self.name, self.age, self.test_Scores)


if __name__ == '__main__':
    stds = list()
    while True:
        inputName = input('Enter name: ')
        inputAge = int(input('Enter age: '))
        inputTestScore = int(input('Enter test score: '))
        std = Student(inputName, inputAge, inputTestScore)
        if inputAge == 0:
            break
        stds.append(std)
    stds.sort(key=lambda s: s.name)
    print(stds)

CodePudding user response：

You need to write the function str for students class.

def __str__(self):
   return '\n'.join(self.stds)

CodePudding user response：

try this =>

class Student:
def __init__(self, name = '', age = 0, test_score = 0):
    self.name = name
    self.age = age
    self.test_Scores = test_score
def __str__(self):
    return "({0},{1},{2})".format(self.name,self.age, self.test_Scores)
def __repr__(self):
    return "({0},{1},{2})".format(self.name,self.age, self.test_Scores)

def __lt__(self, other):
     return self.age < other.age
    
class Students():
    stds = list()
    def __init__(self) -> None:
        pass
    def Input(self):
        while True:
            inputName = input('Enter name: ')
            inputAge = int(input('Enter age: '))
            inputTestScore = int(input('Enter test score: '))
            std = Student(inputName, inputAge, inputTestScore)
            if inputAge == 0:
                break
            self.stds.append(std)
    def __str__(self):
        return str(self.stds)

stds = Students()
stds.Input()
print(stds)
stds.stds.sort(reverse=True)
print(stds)

CodePudding user response：

Define a natural order for the students based on their age using @functools.total_ordering:

import functools


@functools.total_ordering
class Student:
    def __init__(self, name='', age=0, test_score=0):
        self.name = name
        self.age = age
        self.test_Scores = test_score

    def __lt__(self, other):
        return self.age < other.age

    def __str__(self):
        return "({0},{1},{2})".format(self.name, self.age, self.test_Scores)


def test_sorting_students():
    alice: Student = Student("Alice", 21, 86)
    bob: Student = Student("Bob", 19, 75)
    caroline: Student = Student("Caroline", 20, 93)

    students = [alice, bob, caroline]
    students.sort()

    assert students[0] == bob
    assert students[1] == caroline
    assert students[2] == alice

Then just sort them:

print(stds.sort())