Question

I'm trying to sort a list of students from a text file in python(3.7) with three separate sorting functions (Bubble, selection, insert) I'm not sure to why as its not working I'm going to guess its because I'm not using the swap function I built. Every time I run it though I get an error that says the following

Traceback (most recent call last):
  File "C:/Users/tkoto/Desktop/SearchAndSortLab.py", line 146, in <module>
    main()
  File "C:/Users/tkoto/Desktop/SearchAndSortLab.py", line 122, in main
    studentArray.gpaSort()
  File "C:/Users/tkoto/Desktop/SearchAndSortLab.py", line 65, in gpaSort
    if maxgpa[gpa1][2] < maxgpa[gpa2][2]:
TypeError: 'Person' object does not support indexing


Current Code:
class Person(object):
    def __init__(self, name, ID, age, gpa):
        self.name = name
        self.id = ID
        self.age = age
        self.gpa = gpa

    def __str__(self):
        output = "\n\nStudent Record for ID# {}\n".format(self.id)
        output += "Name: {} \nAge: {} \nGPA: {}".format(self.name, self.age, self.gpa)
        return output

####################################################################################################
class List(object):
    def __init__(self):
        self.studentList = []
        self.getList()

    def getList(self):
        try:
            file = open("students.txt", "r")
            name = file.readline().rstrip("\n")
            while len(name) != 0:
                id = int(file.readline().rstrip("\n"))
                age = int(file.readline().rstrip("\n"))
                gpa = float(file.readline().rstrip("\n"))
                self.studentList.append(Person(name, id, age, gpa))
                name = file.readline().rstrip("\n")
        except:
            print("File could not be opened")

    def spaces(self, name):
        tab = 24 - len(name)
        temp = ''
        for j in range(tab):
            temp += " "
        return temp

    def displayStudent(self, index):
        print(self.studentList[index])

    def display(self, listInfo):
        print('\nDisplaying {}'.format(listInfo))
        print("\nStudent ID#      Student Name              Age        GPA")
        print("=============================================================")
        for person in self.studentList:
            print("{}           {}".format(person.id, person.name), self.spaces(person.name),
                  "{}         {}".format(person.age, person.gpa))

    def swap(self, x, y):
        """swap the person objects in the studentList at index x and y"""
        temp = self.studentList[x]
        self.studentList[x] = self.studentList[y]
        self.studentList[y] = temp



    def gpaSort(self):
        """sort the students list in descending order of GPA"""
        """Bubble sort"""


        maxgpa = list(self.studentList)
        for gpa1 in range(len(maxgpa)):
            for gpa2 in range(len(maxgpa)-1):
                if maxgpa[gpa2][0] < maxgpa[gpa2 + 1][0]:
                    maxgpa[gpa2], maxgpa[gpa2 + 1] = maxgpa[gpa2 + 1], maxgpa[gpa2]

        return maxgpa




    def ageSort(self):
        """sort the students list in ascending order of age"""
        """selection sort"""

        minage = list(self.studentList)
        for age1 in range(len(minage)):
            for age2 in range(age1 + 1, len(minage)):
                if minage[age1][2] > minage[age2][2]:
                    minage[age1], minage[age2] = minage[age2], minage[age1]

        return minage

    def idSort(self):
        """sort the student list in descending order of id numbers"""
        """Insertion sort"""

        maxid = list(self.studentList)
        for idindex in range(1, len(maxid)):
            while(idindex > 0):
                if maxid[idindex][3] < maxid[idindex - 1][3]:
                    break
                maxid[idindex], maxid[idindex -1 ] = maxid[idindex - 1], maxid[idindex]
                idindex -= 1

        return maxid

    def search(self, studentID):
        """search for a student in the student list with the passed idNumber
        return the index of the student if found, return -1 if not found"""

        pass




############################################################################################
def main():
    studentArray = List()
    studentArray.display("UNSORTED LIST OF STUDENTS")
    input("\nPRESS ENTER TO SORT BY GPA")

    studentArray.gpaSort()
    studentArray.display("STUDENTS SORTED IN DESCENDING ORDER BY GPA")
    input("\nPRESS ENTER TO SORT BY AGE")

    studentArray.ageSort()
    studentArray.display("STUDENTS SORTED IN ASCENDING ORDER BY AGE")
    input("\nPRESS ENTER TO SORT BY ID#")

    studentArray.idSort()
    studentArray.display("STUDENTS SORTED IN DESCENDING ORDER BY ID#")
    input("PRESS ENTER TO CONTINUE")

    if hasattr(studentArray, "search"):
        try:
            idNumber = int(input("\n\nEnter the ID number of a student to search for: "))
            location = studentArray.search(idNumber)
            if location == -1:
                print("Student Not Found")
            else:
                studentArray.displayStudent(location)
        except ValueError:
            print("Run it again and type an integer value")
    input("\n\nPRESS ENTER TO QUIT")

main()

Answer 1

    def gpaSort(self):
        """sort the students list in descending order of GPA"""
        """Bubble sort"""


        maxgpa = list(self.studentList)
        for gpa1 in range(len(maxgpa)):
            for gpa2 in range(len(maxgpa)-1):
                if maxgpa[gpa2].gpa < maxgpa[gpa2 + 1].gpa:
                    maxgpa[gpa2], maxgpa[gpa2 + 1] = maxgpa[gpa2 + 1], maxgpa[gpa2]

        return maxgpa




    def ageSort(self):
        """sort the students list in ascending order of age"""
        """selection sort"""

        minage = list(self.studentList)
        for age1 in range(len(minage)):
            for age2 in range(age1 + 1, len(minage)):
                if minage[age1].age > minage[age2].age:
                    minage[age1], minage[age2] = minage[age2], minage[age1]

        return minage

    def idSort(self):
        """sort the student list in descending order of id numbers"""
        """Insertion sort"""

        maxid = list(self.studentList)
        for idindex in range(1, len(maxid)):
            while(idindex > 0):
                if maxid[idindex].id < maxid[idindex - 1].id:
                    break
                maxid[idindex], maxid[idindex -1 ] = maxid[idindex - 1], maxid[idindex]
                idindex -= 1

        return maxid


===========================
The issue is in above 3 functions.. When you want to compare the gpa, then you need to say:
"maxgpa[gpa2].gpa" not "maxgpa[gpa2][0]", Because there is no index 0, in person object.. Rather person object has attributes such as id, gpa, name etc.. 

maxgpa is a list of persons.. So when you say maxgpa[gpa2] it means, you got a person object.. On this you say .gpa, which means you are accessing the gpa attribute of person and comparing that.

Please upvote if it helps. Thanks!