ValueError: I/O operation on closed file

[joshuasiler]

I have a multiprocess system that I'm trying to move from Blessings to Blessed. Currently, the code calls term = Terminal() in the main process, and then again in each forked process allowing everyone to write to the screen.

When I changed the import to Blessed, the system now fails on term = Terminal() in the forked processes with the following error:

ValueError: I/O operation on closed file

Any idea why there's a difference in operation?

[jquast]

I'm curious what line number / source code this ValueError raised from? I've been going back & forth on 2 things at this line number, that is maybe relevant:

https://github.com/jquast/blessed/blob/master/blessed/terminal.py#L185

                curses.setupterm(kind, open(os.devnull).fileno())

The previous version is just like blessings was,

                curses.setupterm(self._kind, self._init_descriptor)

which you're welcome to try to see if it makes any difference

[jquast]

I've been seeing this at the end of pytest, I don't know if its similar or not, its just a side-effect I guess,

Exception ignored in: <_io.FileIO name='/dev/null' mode='rb' closefd=True>
Traceback (most recent call last):
  File "/Users/jq/Code/blessed/blessed/terminal.py", line 185, in __init__
    curses.setupterm(self._kind, open(os.devnull).fileno())
ResourceWarning: unclosed file <_io.TextIOWrapper name='/dev/null' mode='r' encoding='UTF-8'>

which goes away if I revert to the previous setupterm(), I'm going to revert this and release a 1.17.2 soon, whether it helps you or not :)

[joshuasiler]

Here is the stack trace, hopefully that helps.

File "/home/ubuntu/dev/AlgoTrader/lib/strategy_runner.py", line 10, in run
    term = Terminal()

File "/home/ubuntu/.local/share/virtualenvs/AlgoTrader-i7wbyDWF/lib/python3.8/site-packages/blessed/terminal.py", line 166, in __init__
    self.__init__streams()

File "/home/ubuntu/.local/share/virtualenvs/AlgoTrader-i7wbyDWF/lib/python3.8/site-packages/blessed/terminal.py", line 237, in __init__streams
    self._keyboard_fd = sys.__stdin__.fileno()

ValueError: I/O operation on closed file

[jquast]

Ah, well, in this case, stdin has some strange issue, we can safely ignore it with the understanding that inkey() and other keyboard functions would not work, you wouldn't be able to use it deep within multiprocessing anyway, this is a shared resource that is getting mucked, thanks for the bug report, i'll try something

[joshuasiler]

So catch the exception and ignore... I'm happy to contribute, should I try to put together a PR for you?

[jquast]

I'm already done and rolling to pypi, #147

[avylove]

@jquast , We probably want to append the exception to errors rather than just pass. That way we have some history when it's not working unexpectedly.

[jquast]

I'm afraid you're too late, you'll have to prepare it for the next release, the twine finished just before I saw your message.

[jquast]

you're welcome to try from pypi @joshuasiler

[joshuasiler]

Updated and it now works. Thanks!