easygui课后作业第四题疑问
import easygui as gimport os
file_path = g.fileopenbox(default="*.txt")
with open(file_path) as old_file:
title = os.path.basename(file_path)
msg = "文件【%s】的内容如下：" % title
text = old_file.read()
text_after = g.textbox(msg, title, text)
if text != text_after[:-1]:
# textbox 的返回值会追加一个换行符
choice = g.buttonbox("检测到文件内容发生改变，请选择以下操作：", "警告", ("覆盖保存", "放弃保存", "另存为..."))
if choice == "覆盖保存":
with open(file_path, "w") as old_file:
old_file.write(text_after[:-1])
if choice == "放弃保存":
pass
if choice == "另存为...":
another_path = g.filesavebox(default=".txt")
if os.path.splitext(another_path) != '.txt':
another_path += '.txt'
with open(another_path, "w") as new_file:
new_file.write(text_after[:-1])
为什么打开文件后，点cancel，会报TypeError？
Traceback (most recent call last):
File "C:/Users/Tina Hu/Desktop/1.py", line 12, in <module>
if text != text_after[:-1]:
TypeError: 'NoneType' object is not subscriptable text_after =g.textbox(msg, title, text)
点击cancel相当于关闭了g.textbox(msg, title, text)
变量text_after就会变为None
在执行text != text_after[:-1]语句时，由于text_after为None，所以不能切片
可以外层嵌套个if来解决
import easygui as g
import os
file_path = g.fileopenbox(default="*.txt")
if file_path:
with open(file_path) as old_file:
title = os.path.basename(file_path)
msg = "文件【%s】的内容如下：" % title
text = old_file.read()
text_after = g.textbox(msg, title, text)
if text_after:
if text != text_after[:-1]:
# textbox 的返回值会追加一个换行符
choice = g.buttonbox("检测到文件内容发生改变，请选择以下操作：", "警告", ("覆盖保存", "放弃保存", "另存为..."))
if choice == "覆盖保存":
with open(file_path, "w") as old_file:
old_file.write(text_after[:-1])
if choice == "放弃保存":
pass
if choice == "另存为...":
another_path = g.filesavebox(default=".txt")
if os.path.splitext(another_path) != '.txt':
another_path += '.txt'
with open(another_path, "w") as new_file:
new_file.write(text_after[:-1])
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