python - 无法使用 pickle 和多个模块加载文件

Question

我正在尝试创建一个使用设置和 Gui 模块的用户系统，当 GUI 模块请求使用 pickle 加载文件时，我不断收到属性错误。这是来自设置模块:

import pickle
import hashlib

class User(object):
    def __init__(self, fname, lname, dob, gender):
        self.firstname = fname
        self.lastname = lname
        self._dob = dob
        self.gender = gender
        self.type = 'General'
        self._username = ''
        self._hashkey = ''

    def Report(self):
        print("Full Name: {0} {1}\nDate of Birth: {2}\nGender: {3}\nAccess Level: {4}".format(self.firstname,self.lastname, self._dob, self.gender, self.type))
        print(self._username)

    def Genusername(self):
        self._username = str(str(self._dob)[:2] + self.firstname[:2] + self.lastname[:2])
        saveUsers(users)

    def Genhashkey(self, password):
        encoded = password.encode('utf-8','strict')
        return hashlib.sha256(encoded).hexdigest()

    def Verifypassword(self, password):
        if self._hashkey == self.Genhashkey(password):
            return True
        else:
            return False

class SAdmin(User):
    def __init__(self, fname, lname, dob, gender):
        super().__init__(fname, lname, dob, gender)
        self.type = 'Stock Admin'

class Manager(User):
    def __init__(self, fname, lname, dob, gender):
        super().__init__(fname, lname, dob, gender)
        self.type = 'Manager'

def saveUsers(users):
    with open('user_data.pkl', 'wb') as file:
        pickle.dump(users, file, -1) # PICKLE HIGHEST LEVEL PROTOCOL

def loadUsers(users):
    try:        
        with open('user_data.pkl', 'rb') as file:
            temp = pickle.load(file)
            for item in temp:
                users.append(item)
    except IOError:
        saveUsers([])

def userReport(users):
    for user in users:
        print(user.firstname, user.lastname)

def addUser(users):
    fname = input('What is your First Name?\n > ')
    lname = input('What is your Last Name?\n > ')
    dob = int(input('Please enter your date of birth in the following format, example 12211996\n> '))
    gender = input("What is your gender? 'M' or 'F'\n >")
    level = input("Enter the access level given to this user 'G', 'A', 'M'\n > ")
    password = input("Enter a password:\n > ")
    if level == 'G':
        usertype = User
    if level == 'A':
        usertype = SAdmin
    if level == 'M':
        usertype = Manager
    users.append(usertype(fname, lname, dob, gender))
    user = users[len(users)-1]
    user.Genusername()
    user._hashkey = user.Genhashkey(password)
    saveUsers(users)

def deleteUser(users):
    userReport(users)
    delete = input('Please type in the First Name of the user do you wish to delete:\n > ')
    for user in users:
        if user.firstname == delete:
            users.remove(user)
    saveUsers(users)

def changePass(users):
    userReport(users)
    change = input('Please type in the First Name of the user you wish to change the password for :\n > ')
    for user in users:
        if user.firstname == change:
            oldpass = input('Please type in your old password:\n > ')
            newpass = input('Please type in your new password:\n > ')
            if user.Verifypassword(oldpass):
                user._hashkey = user.Genhashkey(newpass)
                saveUsers(users)
            else:
                print('Your old password does not match!')

def verifyUser(username, password):
    for user in users:
        if user._username == username and user.Verifypassword(password):
            return True
        else:
            return False  

if __name__ == '__main__':
    users = []
    loadUsers(users)

这是 GUI 模块:

from PyQt4 import QtGui, QtCore
import Settings

class loginWindow(QtGui.QDialog):    
    def __init__(self):
        super().__init__()        
        self.initUI()

    def initUI(self):
        self.lbl1 = QtGui.QLabel('Username')
        self.lbl2 = QtGui.QLabel('Password')
        self.username = QtGui.QLineEdit()
        self.password = QtGui.QLineEdit()

        self.okButton = QtGui.QPushButton("OK")
        self.okButton.clicked.connect(self.tryLogin)
        self.cancelButton = QtGui.QPushButton("Cancel")

        grid = QtGui.QGridLayout()
        grid.setSpacing(10)

        grid.addWidget(self.lbl1, 1, 0)
        grid.addWidget(self.username, 1, 1)
        grid.addWidget(self.lbl2, 2, 0)
        grid.addWidget(self.password, 2, 1)
        grid.addWidget(self.okButton, 3, 1)
        grid.addWidget(self.cancelButton, 3, 0)

        self.setLayout(grid)

        self.setGeometry(300, 300, 2950, 150)
        self.setWindowTitle('Login')
        self.show()

    def tryLogin(self):
        print(self.username.text(), self.password.text())
        if Settings.verifyUser(self.username.text(),self.password.text()):
            print('it Woks')
        else:
            QtGui.QMessageBox.warning(
                self, 'Error', 'Incorrect Username or Password')

class Window(QtGui.QMainWindow):
    def __init__(self):
        super().__init__()        


if __name__ == '__main__':

    app = QtGui.QApplication(sys.argv)
    users = []
    Settings.loadUsers(users)
    if loginWindow().exec_() == QtGui.QDialog.Accepted:
        window = Window()
        window.show()
        sys.exit(app.exec_())

每个用户都是一个类，被放入一个列表中，然后当我只加载设置文件并验证登录时使用 pickle 保存列表，一切正常，但是当我打开 GUI 模块并尝试验证它时不允许我，我得到的错误:

Traceback (most recent call last):
  File "C:\Users`Program\LoginGUI.py", line 53, in <module>
    Settings.loadUsers(users)
  File "C:\Users\Program\Settings.py", line 51, in loadUsers
    temp = pickle.load(file)
AttributeError: Can't get attribute 'Manager' on <module '__main__' (built-in)>

Answer 1

问题是您通过实际运行“设置”模块来挑选设置中定义的对象，然后您试图从GUI 中取消挑选对象模块。

请记住，pickle 实际上并不存储有关类/对象的构造方式的信息，并且在解封时需要访问该类。参见 wiki on using Pickle了解更多详情。

在 pkl 数据中，您看到被引用的对象是 __main__.Manager，因为在您创建 pickle 文件时“设置”模块是 ma​​in(即您运行“设置”模块作为调用 addUser 函数的主脚本)。

然后，您尝试在“Gui”中进行 unpickling - 因此该模块的名称为 __main__，并且您正在该模块中导入设置。因此，Manager 类当然是 Settings.Manager。但是 pkl 文件并不知道这一点，并在 __main__ 中寻找 Manager 类，并抛出一个 AttributeError 因为它不存在(Settings.Manager 存在，但是__main__.Manager 没有)。

下面是用于演示的最小代码集。

class_def.py 模块:

import pickle

class Foo(object):
    def __init__(self, name):
        self.name = name

def main():
    foo = Foo('a')
    with open('test_data.pkl', 'wb') as f:
        pickle.dump([foo], f, -1)

if __name__=='__main__':
    main()

您运行上面的代码以生成 pickle 数据。 main_module.py 模块:

import pickle

import class_def

if __name__=='__main__':
    with open('test_data.pkl', 'rb') as f:
        users = pickle.load(f)

您运行上面的命令以尝试打开 pickle 文件，这将抛出与您看到的大致相同的错误。 (略有不同，但我猜那是因为我使用的是 Python 2.7)

解决方案是:

1. 您通过显式导入使该类在顶级模块(即 GUI 或 main_module)的命名空间内可用，或者
2. 您从与您将在其中打开它的相同的顶级模块创建 pickle 文件(即从 GUI 调用 Settings.addUser，或 class_def.main 来自 main_module)。这意味着 pkl 文件会将对象保存为 Settings.Manager 或 class_def.Foo，然后可以在 GUI`main_module 中找到它们` 命名空间。

选项 1 示例:

import pickle

import class_def
from class_def import Foo # Import Foo into main_module's namespace explicitly

if __name__=='__main__':
    with open('test_data.pkl', 'rb') as f:
        users = pickle.load(f)

选项 2 示例:

import pickle

import class_def

if __name__=='__main__':
    class_def.main() # Objects are being pickled with main_module as the top-level
    with open('test_data.pkl', 'rb') as f:
        users = pickle.load(f)