更正脚本中的Attribute和/或UnboundLocalError

Question

此脚本接受用户输入（对于员工）并通过SQLAlchemy添加到sqlite3 .db。它工作正常，直到我在age_adata方法中为age字段添加try: except子句（计划向其他字段添加更多try / except子句）。 age字段需要是用户选择的int。我意识到我需要一种方法来捕获用户将字符串添加到字段而不是数字所导致的任何错误。相关代码。 。

try:
        self.age = self.age_var.get()
    except ValueError:
        showinfo("Error:", "Please Enter A Number In Age Field.")

然而，当我这样做时，它会产生一个问题，因为age现在变成一个局部变量（正如Backtrack在另一篇文章中指出的那样）而且我得到了UnboundLocalError：局部变量＆＃39; age＆＃39;在分配之前引用。我尝试通过分离检索数据并添加到数据库来更改代码，就像这样。 。

def get_data(self):        
    self.name = self.name_var.get()
    try:
        self.age = self.age_var.get()
    except ValueError:
        showinfo("Error:", "Please Enter A Number In Age Field.")
    self.addr = self.address_var.get()
    self.city = self.city_var.get()
    self.state = self.state_var.get()
    self.zip = self.zip_var.get()   
    self.ssn = self.ssn_var.get()
    self.phone = self.phone_var.get()
    self.cell = self.cell_var.get()

def add_data(self):
    self.get_data()
    # create new Employee in .db
    new_person = Employee(name=self.name, age=self.age, address=self.addr, city=self.city, state=self.state, zip=self.zip, ssn=self.ssn, phone=self.phone, cell=self.cell)
    session.add(new_person)
    session.commit()
    session.close()
    self.callback()
    return

然而，我以不同的方式遇到同样的问题。现在我得到AttributeError: GUI instance has no attribute 'age'。我不确定如何解决这些问题。我尝试在try / except子句self.age=0之前添加一个默认值，以确定错误，但会产生另一个问题。 。如果用户输入的是字符串而不是int，则showinfo框会显示警告，但是当用户点击“确定”时，默认值为＆＃39; 0＆＃39; 0自动添加到数据库，而不是给用户另一个机会输入年龄的数字。当然，我可以将age字段更改为Class Employee中的String，但这不是我想要的。我失去了做什么。任何帮助是极大的赞赏！无论如何，这是原始代码。 。

from datetime import datetime
from Tkinter import *
from tkMessageBox import *
import sqlite3, sqlalchemy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, DateTime, Integer, String, MetaData
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# map classes to tables through Base Class
Base = declarative_base()


class Employee(Base):
    __tablename__ = 'employee'
    id = Column(Integer, primary_key=True)
    name = Column(String(250))
    age = Column(Integer)
    address = Column(String(250))
    city = Column(String(10))
    state = Column(String(2))
    zip = Column(Integer)
    ssn = Column(String(12))
    phone = Column(String(12))
    cell = Column(String(12))

# create engine for Session connection
engine = create_engine('sqlite:///employee.db')

# create all tables in engine ('CREATE TABLE' in raw SQL)
Base.metadata.create_all(engine)

# create configured 'Session' class
Session = sessionmaker(bind=engine)

# create session
session = Session()


class GUI:
    def __init__(self, parent):
        self.parent = parent

        # create top frame
        frame = Frame(parent)
        frame.pack(expand=YES, fill=BOTH, padx=5, pady=5)

        # create bottom frame
        btm_frame = Frame(parent, relief=SUNKEN, borderwidth=1)
        btm_frame.pack(side=BOTTOM, expand=YES, fill=BOTH, padx=5, pady=5)

        # create datetime object
        d = datetime.today()
        date = d.strftime("%Y-%m-%d")


#------------------------Create Labels-------------------------------#


        # label to display date
        date_label = Label(btm_frame, text=date)
        date_label.pack(side=LEFT)

        # name label
        name_label = Label(frame, text="Enter Name:")
        name_label.grid(row=0, sticky=W)

        # age label
        age_label = Label(frame, text="Enter Age:")
        age_label.grid(row=1, sticky=W)

        # address label
        addr_label = Label(frame, text="Enter Address:")
        addr_label.grid(row=2, sticky=W)

        # city label
        city_label = Label(frame, text="Enter City:")
        city_label.grid(row=3, sticky=W)

        # state label
        state_label = Label(frame, text="Enter State:")
        state_label.grid(row=4, sticky=W)

        # zip code label
        zip_label = Label(frame, text="Enter Zip Code:")
        zip_label.grid(row=5, sticky=W)

        # ssn label
        ssn_label = Label(frame, text="Enter Social Security #:")
        ssn_label.grid(row=6, sticky=W)

        # phone label
        phone_label = Label(frame, text="Enter Phone #:")
        phone_label.grid(row=7, sticky=W)

        # cell label
        cell_label = Label(frame, text="Enter Cell #:")
        cell_label.grid(row=8, sticky=W)


#----------------------Create Vars and Entry-------------------------#


        # name variable and entry
        self.name_var = StringVar()
        self.e1 = Entry(frame, textvariable=self.name_var)
        self.e1.grid(row=0, column=1)

        # age variable and entry
        self.age_var =  IntVar()
        self.e2 = Entry(frame, textvariable=self.age_var)
        self.e2.grid(row=1, column=1)

        # address variable and entry
        self.address_var = StringVar()
        self.e3 = Entry(frame, textvariable=self.address_var)
        self.e3.grid(row=2, column=1)

        # city variable and entry
        self.city_var = StringVar()
        self.e4 = Entry(frame, textvariable=self.city_var)
       self.e4.insert(0, "Roanoke")        # insert default value
       self.e4.grid(row=3, column=1)

        # state variable and entry
        self.state_var = StringVar()
        self.e5 = Entry(frame, textvariable=self.state_var)
        self.e5.insert(0, "VA")             # insert default value
        self.e5.grid(row=4, column=1)

        # zip code variable and entry
        self.zip_var = IntVar()
        self.e6 = Entry(frame, textvariable=self.zip_var)
        self.e6.grid(row=5, column=1)

        # s.s.n variable and entry
        self.ssn_var = StringVar()
        self.e7 = Entry(frame, textvariable=self.ssn_var)
        self.e7.grid(row=6, column=1)

    # phone variable and entry
        self.phone_var = StringVar()
        self.e8 = Entry(frame, textvariable=self.phone_var)
        self.e8.grid(row=7, column=1)

        # cell variable and entry
        self.cell_var = StringVar()
        self.e9 = Entry(frame, textvariable=self.cell_var)
        self.e9.grid(row=8, column=1)

        # quit, search, clear, add, delete buttons
        quit_button = Button(btm_frame, text="Quit", relief=GROOVE, command=parent.destroy)
        quit_button.pack(side=RIGHT)        

        search_button = Button(btm_frame, text="Search", relief=GROOVE, command=self.search)
        search_button.pack(side=RIGHT, padx=1, pady=1)

        clear_button = Button(btm_frame, text="Clear", relief=GROOVE, command=self.clear_entries)
        clear_button.pack(side=RIGHT, padx=1, pady=1)        

        del_button = Button(btm_frame, text="Delete", relief=GROOVE, command=self.del_employee)
        del_button.pack(side=RIGHT, padx=1, pady=1)

        add_button = Button(btm_frame, text="Add", relief=GROOVE, command=self.add_data)
        add_button.pack(side=RIGHT, padx=1, pady=1)


    def add_data(self):        
        name = self.name_var.get()
        age = self.age_var.get()        
        addr = self.address_var.get()
        city = self.city_var.get()
        state = self.state_var.get()
        zip = self.zip_var.get()
        ssn = self.ssn_var.get()
        phone = self.phone_var.get()
        cell = self.cell_var.get()
        # create new Employee in .db
        new_person = Employee(name=name, age=age, address=addr, city=city, state=state, zip=zip, ssn=ssn, phone=phone, cell=cell)
        session.add(new_person)
        session.commit()
        session.close()
        self.callback()
        return        

    def callback(self):        
        showinfo("New Employee", "Data Added")
        self.clear_entries()
        return        

    def clear_entries(self):
        entries = [self.e1, self.e2, self.e3, self.e4, self.e5, self.e6, self.e7, self.e8, self.e9]
        for entry in entries:
            entry.delete(0, END)
        return            

    def search(self):
        search_win = Toplevel()
        search_win.title("Employee Search")

        # create labels for each employee attribute
        attr =   ["Id","Name","Age","Address","City","State","Zip","SSN","Cell","Phone"]
        column = 0
        for a in attr:
                Label(search_win, text=a).grid(row=0,column=column,padx=2, pady=2)
                column += 1

        # search all employees, put each emp. in Entry Widget with For Loop
        res = session.query(Employee).all()
        row = 1
        column = 0
        for employee in res:
            txt = [employee.id, employee.name, employee.age, employee.address, employee.city, employee.state, employee.zip, employee.ssn, employee.phone, employee.cell]
            for t in txt:
                ent = Entry(search_win, relief=RIDGE, width=19)
                ent.grid(row=row, column=column, sticky=W, padx=1, pady=1)
                ent.insert(0, t)
                column += 1
            row += 1
            column = 0
        return

    def del_employee(self):
        del_win = Toplevel()
        del_win.title("Delete Employee")

        id_label = Label(del_win, text="Enter Employee Id:")
        id_label.grid(row=0, column=0, padx=5, pady=5)

        self.employee_id = IntVar()
        self.e10 = Entry(del_win, textvariable=self.employee_id)
        self.e10.grid(row=0, column=1, padx=5, pady=5)

        del_button = Button(del_win, text="Delete Employee", relief=GROOVE, command=self.erase)
        del_button.grid(row=0, column=2, padx=5, pady=5)
        return

    def erase(self):
        emp_id = self.employee_id.get()
        res = session.query(Employee).filter(Employee.id==emp_id).first()
        session.delete(res)
        session.commit()
        showinfo("Employee", "Data Deleted")
        return



if __name__ == '__main__':
    root = Tk()
    root.geometry("310x270")
    root.title("Employee Info")
    mygui = GUI(root)
    root.mainloop()

这是我在更改上面的代码后得到的第一个错误，将try：except子句添加到add_data方法中的age变量。 。换句话说，将上面的add_data方法更改为：

def add_data(self):        
    name = self.name_var.get()
    try:
        age = self.age_var.get()
    except ValueError:
        showinfo("Error:", "Please Enter A Number In Age Field.")
    addr = self.address_var.get()
    city = self.city_var.get()
    state = self.state_var.get()
    zip = self.zip_var.get()   
    ssn = self.ssn_var.get()
    phone = self.phone_var.get()
    cell = self.cell_var.get()
    # create new Employee in .db
    new_person = Employee(name=name, age=age, address=addr, city=city, state=state, zip=zip, ssn=ssn, phone=phone, cell=cell)
    session.add(new_person)
    session.commit()
    session.close()
    self.callback()
    return

当用户在年龄字段中输入字符串然后单击＆＃34;确定＆＃34;时，我收到此错误在showinfo对话框中）：

    Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 1532, in __call__
    return self.func(*args)
  File "C:\Python27\test2_gui.py", line 182, in add_data
    new_person = Employee(name=name, age=age, address=addr, city=city, state=state, zip=zip, ssn=ssn, phone=phone, cell=cell)
UnboundLocalError: local variable 'age' referenced before assignment

Answer 1

在你的问题开始时，你有一段代码，然后你跟着它，“age现在变成一个局部变量”。这是不可能的，因为a）你展示的代码既没有设置也没有使用名为age的变量，而b）这不是尝试的。您的代码集self.age，但这与名为age的局部变量完全不同。

错误消息告诉您需要知道的所有内容。如果它说“在分配前引用了”局部变量'年龄'，那么你可以相信它正在讲述字面上的事实。您必须问自己“为什么age（不 self.age）当我认为它是全局的？”或“为什么age未设置？当我认为它是什么时候？“ 一个try语句本身将_not_神奇地将变量设为本地。

让我重复最后一行：一个try语句本身将_not_神奇地使变量本地化。你在评论中链接的另一个答案给了你不好的建议。

理解正在发生的事情的一种简单的低技术方法是在分配局部变量age之后立即放置一个print语句，并且您将看到该行代码未被执行。你需要逐步完成逻辑，看看它为什么没有被执行。

如果真正的问题是它抱怨局部变量age并且您正在设置名为self.age的属性，那就是问题 - 将age更改为self.age再次，在你正在设置self.age的位置放置一个打印语句，以证明它是 - 或者没有 - 在你收到错误之前被设置。

不幸的是，你弄得一团糟。我认为有几个不同版本的代码，以及与“原始版本”一致的错误消息，并且当前版本没有错误。我认为。这真的很难理解。

可能问题很简单，如果你的try在设置变量时遇到错误，那么该变量就不会被设置。如果try之后有其他代码并使用该变量，则它将失败，因为try块无法设置变量。一个简单的解决方案可能是在catch块中将变量设置为零。