Python列表append操作覆盖已有字典问题求助

问题描述 #

我是Python新手，编写了一段程序，旨在接收员工输入信息并存入字典，再将该字典存入列表。但每次循环时，列表中已存储的字典都会被新字典覆盖。

原代码 #

total_properties_sold = 0
total_commission = 0
bonus_pay = 0
employees = [] #empty list to store dictonary of employees information
employee = {} #empty dictonary to store the information of employees

while True:
    number_of_employees = input("Enter number of employees who have worked this week: ")
    if number_of_employees.isdigit(): #validation check to ensure input is a digit
        number_of_employees = int(number_of_employees) #if input is digit, convert to int
        if number_of_employees >= 2 and number_of_employees <= 5: #validates the range of input
            break
        else:
            print("Input invalid... enter a digit\n")
            
    else:
        print("Input invalid... enter a digit\n")
        

#for loop to enter the details of the number of employees
for number in range(number_of_employees):
    name = input("Enter employee name: ")

    while True: #validation check to ensure input is a digit
        id = input("Enter employee id: ")
        if id.isdigit():
            id = int(id)
            break
        else:    
            print("Invalid data type... enter a number\n")

    while True:
        properties_sold = input("enter number of properties sold by employee: ")
        if properties_sold.isdigit():
            properties_sold = int(properties_sold)
            break
        else: 
            print("Invalid data type... enter a number")

    total_properties_sold += properties_sold #calculates the total properties sold this week
    employee_commission = properties_sold * 500 
    employee_commission = float(employee_commission) #converts commission into a float
    total_commission += employee_commission #calculates the total commission this week
    total_commission = float(total_commission) #converts total commission into float

    #add employee information into the employee dictonary
    employee["name"] = name
    employee["employee id"] = id
    employee["properties sold"] = properties_sold
    employee["commission"] = employee_commission

    employees.append(employee) #adding the employee dictonary into employees list
    
    print(employees)

预期输出 #

[{'name': 'employee1', 'employee id': 1, 'properties sold': 4, 'commission': 2000.0}, {'name': 'employee2', 'employee id': 2, 'properties sold': 3, 'commission': 1500.0}, {'name': 'employee3', 'employee id': 3, 'properties sold': 10, 'commission': 5000.0}]

实际输出 #

[{'name': 'employee3', 'employee id': 3, 'properties sold': 10, 'commission': 5000.0}, {'name': 'employee3', 'employee id': 3, 'properties sold': 10, 'commission': 5000.0}, {'name': 'employee3', 'employee id': 3, 'properties sold': 10, 'commission': 5000.0}]

问题原因 #

你只在循环外创建了一个employee字典对象，每次循环只是修改这个对象的键值对，列表中添加的都是同一个字典的引用。所有列表元素指向的都是同一个内存地址的字典，所以最后所有元素都会显示最后一次修改的内容。

解决方法 #

将employee = {}移到for循环内部，每次循环都创建一个新的字典对象，这样添加到列表中的每个字典都是独立的，不会互相覆盖。

修改后的代码 #

total_properties_sold = 0
total_commission = 0
bonus_pay = 0
employees = [] #empty list to store dictonary of employees information

while True:
    number_of_employees = input("Enter number of employees who have worked this week: ")
    if number_of_employees.isdigit(): #validation check to ensure input is a digit
        number_of_employees = int(number_of_employees) #if input is digit, convert to int
        if number_of_employees >= 2 and number_of_employees <= 5: #validates the range of input
            break
        else:
            print("Input invalid... enter a digit\n")
            
    else:
        print("Input invalid... enter a digit\n")
        

#for loop to enter the details of the number of employees
for number in range(number_of_employees):
    employee = {} # 每次循环创建新的字典
    name = input("Enter employee name: ")

    while True: #validation check to ensure input is a digit
        id = input("Enter employee id: ")
        if id.isdigit():
            id = int(id)
            break
        else:    
            print("Invalid data type... enter a number\n")

    while True:
        properties_sold = input("enter number of properties sold by employee: ")
        if properties_sold.isdigit():
            properties_sold = int(properties_sold)
            break
        else: 
            print("Invalid data type... enter a number")

    total_properties_sold += properties_sold #calculates the total properties sold this week
    employee_commission = properties_sold * 500 
    employee_commission = float(employee_commission) #converts commission into a float
    total_commission += employee_commission #calculates the total commission this week
    total_commission = float(total_commission) #converts total commission into float

    #add employee information into the employee dictonary
    employee["name"] = name
    employee["employee id"] = id
    employee["properties sold"] = properties_sold
    employee["commission"] = employee_commission

    employees.append(employee) #adding the employee dictonary into employees list
    
    print(employees)

内容的提问来源于stack exchange，提问作者Rohail