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

先重現 issue 中關於已關閉檔案的兩個範例，接著檢查 io.IOBase.readable() 和 writable() 進入點及其相關測試。完成的標準是，這兩個方法對已關閉檔案具有一致且有文件記載的行為，同時保留對開啟檔案的預期結果。