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,并被放入一个列表,然后使用pickle保存列表,当我加载只是设置文件并验证登录一切正常,但当我打开gui模块并尝试验证它不让我,错误我得到:

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"模块来腌制在"设置"中定义的对象,然后您尝试从GUI模块中取消对象的取消.

请记住,pickle实际上并不存储有关如何构造类/对象的信息,并且在unpickling时需要访问该类.有关详细信息,请参阅使用Pickle的wiki.

在pkl数据中,您看到被引用的对象是__main__.Manager,因为创建pickle文件时"设置"模块是主要的(即您将'Settings'模块作为主脚本运行以调用该addUser函数).

然后,您尝试在'Gui'中进行unpickling - 以便模块具有名称__main__,并且您正在该模块中导入Setting.所以当然Manager类实际上也是Settings.Manager.但是pkl文件不知道这一点,并查找其中的Manager类__main__,并抛出一个AttributeError,因为它不存在(Settings.Manager确实存在,但__main__.Manager不存在).

这是一个最小的代码集来演示.

该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()

您运行上面的操作来生成pickle数据.该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)

您运行以上操作以尝试打开pickle文件,这会抛出与您看到的大致相同的错误.(略有不同,但我猜这是因为我在Python 2.7上)

解决方案是:

1. 您可以通过显式导入使该类在顶级模块的命名空间(即GUI或main_module)中可用,或者
2. 您可以从与其打开的模块相同的顶级模块创建pickle文件(即Settings.addUser从GUI 调用或class_def.main从main_module调用).这意味着pkl文件将对象保存为Settings.Manageror class_def.Foo,然后可以在GUI`main_module`命名空间中找到它.

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)

Answer 2

请先阅读zehnpaard提到的答案,了解属性错误的原因.除了他已提供的解决方案之外,python3您可以使用pickle.Unpickler该类并覆盖find_class下面提到的方法:

import pickle

class CustomUnpickler(pickle.Unpickler):

    def find_class(self, module, name):
        if name == 'Manager':
            from settings import Manager
            return Manager
        return super().find_class(module, name)

pickle_data = CustomUnpickler(open('file_path.pkl', 'rb')).load()

Answer 3

如果即使在加载模块中导入适当的类（ zehnpaard 的解决方案#1）后仍然出现此错误，则可以覆盖find_class的函数pickle.Unpickler并显式指示在当前模块的命名空间中查找。

import pickle
from settings import Manager

class CustomUnpickler(pickle.Unpickler):

    def find_class(self, module, name):
        try:
            return super().find_class(__name__, name)
        except AttributeError:
            return super().find_class(module, name)

pickle_data = CustomUnpickler(open('file_path.pkl', 'rb')).load()
## No exception trying to get 'Manager'

注意：此方法会丢失存储在module. 因此，请注意 pickled 类中的名称空间冲突。