用python写一个记事本，打开文件，出现错误
记事本项目
from tkinter.colorchooser import *
from tkinter .filedialog import *
class Application(Frame):
def init(self, master=None):
super().__init__(master) # super()代表父类的定义，而不是父类对象
self .master = master
self .textpad = None # textpad表示Text文本框对象
self .filename = None # filename表示打开文件的名字
self .contextMenu = None # contextMenu表示上下文菜单对象
self .pack()
self .createWidget()
def createWidget(self):
# 创建主菜单
menuber = Menu(root)
# 创建子菜单
menuFile = Menu(menuber)
menuEdit = Menu(menuber)
menuHelp = Menu(menuber)
# 将子菜单加入到主菜单栏
menuber .add_cascade(label='文件(F)', menu=menuFile)
menuber .add_cascade(label='编辑(E)', menu=menuEdit)
menuber .add_cascade(label='帮助(H)', menu=menuHelp)
# 添加菜单项
menuFile .add_command(label='新建', accelerator='ctrl+n', command=self.newfile)
menuFile .add_command(label='打开', accelerator='ctrl+o', command=self.openfile)
menuFile .add_command(label='保存', accelerator='ctrl+s', command=self.savefile)
menuFile .add_separator() # 添加分割线
menuFile .add_command(label='退出', accelerator='ctrl+q', command=self.exit)
# 将主菜单加到根窗口
root['menu'] = menuber
# 添加快捷键处理
root .bind('<Control-n>', lambda event: self .newfile())
root .bind('<Control-o>', lambda event: self .openfile())
root .bind('<Control-s>', lambda event: self .savefile())
root .bind('<Control-q>', lambda event: self .exit())
# 文本编辑区
self .textpad = Text(root, width=50, height=30).pack()
# 上下菜单
self .contextMenu = Menu(root)
self .contextMenu .add_command(label='背景颜色', command=self.openAskColor)
# 为右键绑定事件
root .bind('<Button-3>', self .createContextMenu)
def newfile(self):
pass
def openfile(self):
self .textpad .delete(1.0, END)
with askopenfile(title='文本文件')as f:
#print(f .read()) # 在控制界面打印
self .textpad .insert(INSERT, f .read())
self .filename = f .name
def savefile(self):
with open(self .filename, 'w')as f:
c = self .textpad.get(1.0, END)
f .write(c)
def exit(self):
root .quit()
def createContextMenu(self,event):
# 菜单在鼠标右键的坐标处显示
self .contextMenu.post(event.x_root, event.y_root)
def openAskColor(self):
s1 = askcolor(title='选择背景色', color='red')
self .textpad.config(bg=s1[1])
if name == '__main__':
root = Tk()
root .geometry('450x300+200+300')
root .title('记事本')
app = Application(master=root)
root .mainloop()
出现报错
File "D:/Users/86135/PycharmProjects/gui2/mypy05.py", line 53, in openfile
self .textpad .delete(1.0, END)
AttributeError: 'NoneType' object has no attribute 'delete'
初学者刚刚学python，查找过百度，不知道怎么解决
