Honor PyOS_InputHook in the new REPL about cpython

[mdboom]

Here's a good reproducer to ensure your changes are working (on Linux):

(make install is required to get pkgconfig working for all the dependencies).

$ pip install git+https://github.com/python-pillow/Pillow@d879f39
$ pip install matplotlib

$ python
>>> import matplotlib
>>> matplotlib.use("tkagg")
>>> from matplotlib import pyplot as plt
>>> plt.plot([1,2], [3,4])
[<matplotlib.lines.Line2D object at 0x7fd3f2be8050>]
>>> plt.show(block=False)
>>>

If working, a window should appear with a plot in it, and it should respond to mouse events etc. It seems that on CPython main, this is broken, but works with PYTHON_BASIC_REPL=1 set.

Cc: @tacaswell, do I have this right? IIUC this works due to Tkinter's built-in use of PyOS_InputHook, matplotlib itself doesn't touch it.

EDIT: See a simpler reproducer below

[mdboom]

With #119843 (currently), this fails with:

>>> Fatal Python error: _PyThreadState_Attach: non-NULL old thread state
                                                                        Python runtime state: initialized

                                                                                                         Current thread 0x00007fad7b63c740 (most recent call first):
                                        File "/home/mdboom/py/lib/python3.14/_pyrepl/reader.py", line 713 in call_PyOS_InputHook
    File "/home/mdboom/py/lib/python3.14/_pyrepl/reader.py", line 648 in handle1
                                                                                  File "/home/mdboom/py/lib/python3.14/_pyrepl/reader.py", line 692 in readline
                                   File "/home/mdboom/py/lib/python3.14/_pyrepl/readline.py", line 376 in multiline_input
                                                                                                                           File "/home/mdboom/py/lib/python3.14/_pyrepl/simple_interact.py", line 176 in run_multiline_interactive_console
                                                                                                              File "/home/mdboom/py/lib/python3.14/_pyrepl/__main__.py", line 48 in interactive_console
                                                                           File "/home/mdboom/py/lib/python3.14/_pyrepl/__main__.py", line 51 in <module>
                             File "<frozen runpy>", line 88 in _run_code
                                                                          File "<frozen runpy>", line 198 in _run_module_as_main

  Extension modules: numpy.core._multiarray_umath, numpy.core._multiarray_tests, numpy.linalg._umath_linalg, numpy.fft._pocketfft_internal, numpy.random._common, numpy.random.bit_generator, numpy.random._bounded_integers, numpy.random._mt19937, numpy.random.mtrand, numpy.random._philox, numpy.random._pcg64, numpy.random._sfc64, numpy.random._generator, PIL._imaging, kiwisolver._cext, PIL._imagingmath, PIL._imagingtk (total: 17)
                                                     [1]    3965 IOT instruction  python

[mdboom]

Here's a much easier reproducer with no external dependencies:

from tkinter import *
root = Tk()
w = Label(root, text='Foo')
w.pack()

Current behavior I'm seeing:

CPython main: No window
CPython main / PYTHON_BASIC_REPL=1: Window is displayed, updated automatically with each line of entry (matches 3.12)
#119843: Fatal Python error: _PyThreadState_Attach: non-NULL old thread state
#119843 / PYTHON_BASIC_REPL=1: Window is displayed, updated automatically with each line of entry (matches 3.12)

[tacaswell]

@mdboom Correct. PyQt, wxpython, and the gtk bindings all provide their own verision of PyOS_InputHook as well and mpl provides one for macOSX.

To be 100% sure the event loop is running as expected also add a "print on click" callback:

from tkinter import *
root = Tk()
b = Button(root, text='bar', command=lambda: print('bob'))
w = Label(root, text='Foo')
b.pack()
w.pack()