python3使用tkinter实现txt 阅读、保存、另存功能（简易），最近历史记录

[code]#文本文件的打开,保存和另存；可一键访问历史记录（五个最近的历史记录（不重复））。
import tkinter as tk
#文件选择对话框
import os,json
import tkinter.filedialog
from tkinter import messagebox
#主窗口
root  =tk.Tk()
root.title("Text reader made by yy")
root.geometry('500x500')
##输入窗口（仅仅用作显示）
res = tk.Variable()
entry = tk.Entry(root,textvariable = res,width = 40)
res.set('Selected files:')
entry.pack()

def add_path(path1):
global path_list
try:
with open('C:\yy.txt','r') as f:
path_list = json.load(f)
if path1 not in path_list:
while len(path_list) > 4:
path_list = path_list[1:]
else:
path_list.append(path1)
else:
pass
with open('C:\yy.txt', 'w') as f:
json.dump(path_list, f)
except:
with open('C:\yy.txt','w') as f:
path_list = []
path_list.append(path1)
json.dump(path_list,f)

#初始化列表长度
try:
with open('C:\yy.txt', 'r') as f:
path_list = json.load(f)
if len(path_list) < 5:
while True:
path_list.append('C:')
if len(path_list) >= 5:
break
except:
path_list = []

def func1():		#open
global filename,res
filename = tkinter.filedialog.askopenfilename(filetypes = [(" please open txt file", "*.txt")])
add_path(filename)
try:
with open(filename,'r') as f:
content = f.read()
text.delete(0.0,tk.END)
text.insert(tk.INSERT,content)
basename = os.path.basename(filename)
res.set('%s'%basename)
button4.config(text = os.path.basename(path_list[-1]))
button5.config(text = os.path.basename(path_list[-2]))
button6.config(text = os.path.basename(path_list[-3]))
button7.config(text = os.path.basename(path_list[-4]))
button8.config(text = os.path.basename(path_list[-5]))

except:
pass

def func2():		#save
with open(filename,'w') as f:
try:
f.write(text.get(0.0,tk.END))
f.flush()
basename = os.path.basename(filename)
save_succed = messagebox.showinfo(title='message', message='%s  save succed' % basename)
print(save_succed)
except:
save_error = messagebox.showinfo(title = 'unfortunately ',message = 'save failure')
print(save_error)

#打开历史记录对应的文件
def func3(button,filename):		#open
global res,button4
add_path(filename)
try:
with open(filename,'r') as f:
content = f.read()
text.delete(0.0,tk.END)
text.insert(tk.INSERT,content)
basename = os.path.basename(filename)
res.set('%s'%basename)
except:
pass

def save_as():
filename1 = tkinter.filedialog.asksaveasfilename()
add_path(filename1)
with open(filename1, 'w') as f:
f.write(text.get(0.0, tk.END))
basename = os.path.basename(filename1)
save_succed = messagebox.showinfo(title='message', message='%s  saveas  succed' % basename)
print(save_succed)
#制作底部框体和（打开保存另存）按钮
fm2 = tk.Frame(root)
button1 = tk.Button(fm2,text = 'open',command = func1)
button1.pack(side = "left")

button2 = tk.Button(fm2,text = 'save',command = func2)
button2.pack(side = "left")

button3 = tk.Button(fm2,text = 'saveas',command = save_as)
button3.pack(side = "left")

fm2.pack(side = 'bottom')

#制作右侧的历史记录按钮按钮

#右侧总框架
fm3 = tk.Frame(root)
#右侧label
label_right = tk.Label(fm3,text  = '历史记录 :')
label_right.pack(side = 'top')
#历史文件访问地址获取，通过path_list
a,b,c,d,e = os.path.basename(path_list[-1]),os.path.basename(path_list[-2]),os.path.basename(path_list[-3]),os.path.basename(path_list[-4]),os.path.basename(path_list[-5])
#右侧历史记录的键
#注意lambda花式传参方式
button4 = tk.Button(fm3,text = a,command = lambda func1 = func3:func3(button4,path_list[-1]))
button4.pack(side = "top")

button5 = tk.Button(fm3,text = b,command = lambda func1 = func3:func3(button5,path_list[-2]))
button5.pack(side = "top")

button6 = tk.Button(fm3,text = c,command = lambda func1 = func3:func3(button6,path_list[-3]))
button6.pack(side = "top")

button7 = tk.Button(fm3,text = d,command = lambda func1 = func3:func3(button6,path_list[-4]))
button7.pack(side = "top")

button8 = tk.Button(fm3,text = e,command = lambda func1 = func3:func3(button6,path_list[-5]))
button8.pack(side = "top")

fm3.pack(side = 'right')

#滚动条
scroll = tk.Scrollbar()
scroll.pack(side = tk.RIGHT,fill = tk.Y)
#文本
text = tk.Text(root,width = 200,height = 20)
text.pack(side = tk.LEFT,fill = tk.Y)
#滚动条和文本相互绑定
scroll.config(command = text.yview)
text.config(yscrollcommand = scroll.set)

root.mainloop()