[issue45934] python curses newterm implementation

[Julius Hamilton]

Julius Hamilton <juliushamilton100 at gmail.com> added the comment:

I’m trying to patch this bug.

Here are my current working questions:

1. What is the relationship between an fd (file descriptor) and a terminal? What software / hardware component goes to “fd 0” to receive input from it? Is there a GNU Screen command to receive stdin from “fd n”, fd 3 for example?

2. Looking at the source code:

def initscr():
    import _curses, curses
    # we call setupterm() here because it raises an error
    # instead of calling exit() in error cases.
    setupterm(term=_os.environ.get("TERM", "unknown"),
              fd=_sys.__stdout__.fileno())
    stdscr = _curses.initscr()
    for key, value in _curses.__dict__.items():
        if key[0:4] == 'ACS_' or key in ('LINES', 'COLS'):
            setattr(curses, key, value)

    return stdscr

- why does initscr() begin by importing _curses and curses? Precompiled C curses and non-compiled C or is the second importing Python? How can a module be importing itself?

- they call “setupterm”, a C curses function, because it raises an error if there’s a problem in case of just quitting. But how so, specifically? Do the errors get detected at stderr and then the terminal raises another error or something? I’m not clear on the details. Plus, why can they call this function without referring to the enclosing package, curses.setupterm? Is that a C thing that all functions are automatically added to the namespace?

- Someone wrote that “initscr” actually calls “newterm”, in the code. So I guess I should look at the C newterm code, see how it works and see if a direct implementation is possible.


(I said in an email I would double post an email I sent but instead I’m posting more specific questions here related to that email. Also, I’m still studying an email Guido sent, so apologies for any redundant questions here.)

Thanks,
Julius

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45934>
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