在 python 中写入文件和读取文件

Question

import random

class Student:
    #easy way or short way to printing student details
    def student_details(self):
        print("Student number :",self.student_number)
        print("-----------")
        print("First Name : ",self._firstname)
        print("-----------")
        print("Last Name : ",self._lastname)
        print("-----------")
        print("Date Of Birth : ",self._date_of_birth)
        print("-----------")
        print("Gender : ",self._sex )
        print("-----------")
        print("Country of birth : ",self._country)
    
    #constructor for the class and assign the variables(eg:firstname)
    def __init__(self,firstname,lastname,date_of_birth,sex,country):
        self.student_number = random.randint(1,18330751)
        self._firstname = firstname
        self._lastname = lastname
        self._date_of_birth = date_of_birth
        self._sex = sex
        self._country = country    
        
    
    def get_firstname(self):
        return self._firstname
    
    def set_firstname(self,firstname):
        self._firstname = firstname
   
    def get_lastname(self):
        return self._lastname
    
    def set_lastname(self,lastname):
        self._lastname = lastname
    
    def get_date_of_birth(self):
        return self._date_of_birth
    
    def set_date_of_birth(self,date_of_birth):
        self._date_of_birth = date_of_birth
   
    def get_sex(self):
        return self._sex
    
    def set_sex(self,sex):
        self._sex = sex
   
    def get_country(self):
        return self._country

    
    def set_country(self,country):
        self._country = country
    #this method for converting object when writing to file and reading the file
    def __str__(self):
        return f"{firstname,lastname,date_of_birth,sex,country}"

student = []


while True:
    print("1. Enter 1 and you are going Write the contents of the student array to a file")
    print("-----------")
    print("2.Read student data from a file and populate the student array.")
    print("-----------")
    print("3.Add a new student")
    print("-----------")
    print("4. Enter 4 and you are going to see all students information")
    print("-----------")
    print("5. Enter 5 and you are going to write born year to find students who born in this year")
    print("-----------")
    print("6. Enter 6 and you are going to modify a student record by typing student number because you can't change student number")
    print("-----------")
    print("7. Enter 7 and you are going to write student number to delete student")
    print("-----------")
    print("8. Enter 8 and exit the program")
    print("-----------")
    print("You can choose what to do")
    
    option = int(input("Please write your option: "))
    print("-----------")
    
    if option == 1:
        
     f = open("cmse318.txt","w")
     
     for data in student:
                f.write(data)

                print("-----------")
                print("Successfully write to a  file!!")
                print("-----------")
                break
       
     f.close()
    
    if option == 2:
        f = open("cmse318.txt","r")
        
        for ln in f:
            firstname,lastname,date_of_birth,sex,country = ln.split(",")
            s = Student(firstname,lastname,date_of_birth,sex,country)
            student.append(s)
            print(s)
           
        f.close()

    
    if option == 3:
         firstname,lastname,date_of_birth,sex,country = map(str,input("Please Enter student details like this(cemal,göymen,2000,male,cyprus) : ").split(","))
         s = Student(firstname,lastname,date_of_birth,sex,country)
         student.append(s)
         print("-----------")
         print('Student created successfully!!')
         print("-----------")
         print("-----------")
         
    
    if option == 4 :
        for st in student:
            st.student_details()
            print("-----------")
            print("For now these are the students")
            print("-----------")
            
    
    if option == 5:
        year1 = int(input("Enter year to show students who born in this year(eg:2000): "))
        for dob in student:
            if (int(dob.get_date_of_birth()) == year1):
                
                dob.student_details()
                print("-----------")
                print("All students who born in ", year1)
                print("-----------")
                
    
    if option == 6:
        snr = int(input("Enter a student number: "))
        for sn in student:
            if sn.student_number == snr:
                firstname,lastname,date_of_birth,sex,country = map(str,input("Please Enter student details like this(cemal,göymen,2000,male,cyprus) :").split(","))
                sn.set_firstname(firstname)
                sn.set_lastname(lastname)
                sn.set_date_of_birth(date_of_birth)
                sn.set_sex(sex)
                sn.set_country(country)
                print("-----------")
                print("Student modify success")
                print("-----------")
                
    
    if option == 7:
        snr = int(input("Enter the student number to be deleted : "))
        for sn in student:
            if sn.student_number == snr:
                temp = sn
        student.remove(temp)
        print("-----------")
        print("Student deleted successfully")
        print("-----------")
        
    if option == 8:
        break

I need help in option 1 and option 2 about reading and writing file. In the reading file it does not read all students from a file it reads just one student and ıf there is more than one student in the file it gives an error. In the writing to file part, the problem is I cannot write the student array to file it just write the last element from the student array but I need all elements from my student array.

Answer 1

Code can be improved as follows.

import random
    
class Student:
    def __init__(self,firstname,lastname,date_of_birth,sex,country,student_number = None):
        # reuse student number when we read from file (i.e. if specified)
        # set new one if we don't have one
        self.student_number = student_number or random.randint(1,18330751) # or causes use of rand value 
                                                                           # if student_number = None
        self._firstname = firstname
        self._lastname = lastname
        self._date_of_birth = date_of_birth
        self._sex = sex
        self._country = country    
        
    def student_details(self):
        return (f"Student number : {self.get_student_number()}\n"
                f"-----------  First Name : {self.get_firstname()}\n"
                f"-----------  Last Name : {self.get_lastname()}\n"
                f"-----------  Date Of Birth : {self.get_date_of_birth()}\n"
                f"-----------  Gender : {self.get_sex()}\n"
                f"-----------  Country of birth : {self.get_country()}")
        
    def get_firstname(self):
        return self._firstname
    
    def set_firstname(self,firstname):
        self._firstname = firstname
   
    def get_lastname(self):
        return self._lastname
    
    def set_lastname(self,lastname):
        self._lastname = lastname
    
    def get_date_of_birth(self):
        return self._date_of_birth
    
    def set_date_of_birth(self,date_of_birth):
        self._date_of_birth = date_of_birth
   
    def get_sex(self):
        return self._sex
    
    def set_sex(self,sex):
        self._sex = sex
   
    def get_country(self):
        return self._country

    def set_country(self,country):
        self._country = country
        
    def get_student_number(self):
        return self.student_number
    
    def __str__(self):
        ' For serializing attributes to string --useful for writing to file '
        return (f"{self.get_student_number()},"
                f"{self.get_firstname()},"
                f"{self.get_lastname()},"
                f"{self.get_date_of_birth()},"
                f"{self.get_sex()},"
                f"{self.get_country()}")

def get_student_info():
   ' Use helper function to ensure student entry has correct number of fields '
    while True:
        while True:
            entry = input('''Please Enter student details comma delimited like this (firstname,lastname,date of birth,gender,country)
                            Example Emal,Göymen,4/15/2000,Male,Cyprus : ''')
            fields = entry.split(',')
            if len(fields) == 5:
                # Correct number of fields
                return fields
            else:
                print(f'Entry {entry} incorrecst format')
                print('Shoulbe be five comma delimitede fields i.e. firstname,lastname,date of birth,gender,country')
                

students = []

while True:
    print('''
            1. Write the contents of the student array to a file
                -----------
            2. Read student data from a file and populate the student array.
                -----------
            3. Add a new student
                -----------
            4. Display all students information
                -----------
            5. Information for students born in a particular year
                -----------
            6. Modify student record (you need to know student number)
                -----------
            7. Delete a student (you need to know student number)
                -----------
            8. Exit program
                -----------
            Enter option''')
    
    option = int(input("Please write your option: "))
    print("-----------")
   
    if option == 1:
        with open("cmse318.txt", "w") as f:
            for st in students:
                f.write(str(st) + '\n')
            print("-----------\nSuccessfully wrote to a  file!!\n-----------")
       
    if option == 2:
        with open("cmse318.txt","r") as f:
            students = []  # Start new student array
            for ln in f:
                student_number,firstname,lastname,date_of_birth,sex,country = ln.rstrip().split(",") # rstrip remove '\n' at end of line
                student_number = int(student_number)
                s = Student(firstname,lastname,date_of_birth,sex,country,student_number)
                students.append(s)
                print(str(s))
           
    if option == 3:
        firstname,lastname,date_of_birth,sex,country = get_student_info()
        s = Student(firstname,lastname,date_of_birth,sex,country)
        students.append(s)
        print('''-----------
                Student created successfully!!
                -----------
                -----------''')
         
    if option == 4 :
        print('''-----------
                For now these are the students
                -----------
                -----------''')

        for st in students:
            print(st.student_details())
            
    if option == 5:
        birth_year = input("Enter year to show students who born in this year(eg:2000): ")
        
        print("-----------"
              f"All students who born in {birth_year}"
              "-----------")
        for st in students:
            if birth_year in st.get_date_of_birth():  # e.g. birth_year = 2000, date_of_birth = "May 5, 2000" we get a match
                print(st.student_details())
                
    if option == 6:
        snr = int(input("Enter a student number: "))
        for sn in students:
            if sn.student_number == snr:
                firstname,lastname,date_of_birth,sex,country = get_student_info()
                sn.set_firstname(firstname)
                sn.set_lastname(lastname)
                sn.set_date_of_birth(date_of_birth)
                sn.set_sex(sex)
                sn.set_country(country)
                print("-----------\nStudent modify success\n-----------")
                break
        else:
            print(f"Student number {snr} not found!!!")
                
    
    if option == 7:
        snr = int(input("Enter the student number to be deleted : "))
        # Normally bad practice to delete elements in list while iterating over it, 
        # but in this case we are only deleting a single element so okay
        for sn in students:
            if sn.student_number == snr:
                students.remove(sn)
                print(f"-----------\nStudent {snr} deleted successfully")
                break
        else:
            print("Student {snr} not found")
        
    if option == 8:
        print('Exiting')
        break