Inconsistant behavior of .readable() and .writable() on io.IOBase

Bug report

The methods .readble() and .writable() on io.IOBase should return a boolean representing if the file can be read from/written to. However, calling .readable() on a closed IO file object causes a ValueError, whereas calling .writable() on a closed file returns False if the file was opened with just read permissions, but raises ValueError if it was opened with read and write permissions.

Make a folder with a text file in, then run:

f = open("hello.txt")
print(f.writable())
print(f.readable())
f.close()
print(f.writable())
print(f.readable())

This will output:

False
True
False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file

Then doing a similar thing, but with w+ permissions

f = open("hello.txt", "w+")
print(f.writable())
print(f.readable())
f.close()
print(f.writable())
print(f.readable())

Will output

True
True
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file

Your environment

• CPython versions tested on: 3.10.4
• Operating system and architecture: Windows 64bit

首先复现 issue 中关于已关闭文件的两个示例，然后检查 io.IOBase.readable() 和 writable() 入口点及其相关测试。完成的标准是，这两个方法对已关闭文件具有一致且有文档记录的行为，同时保留对打开文件的预期结果。