`termwinsize` cannot be accessed from Python 3

Question

The option termwinsize cannot be accessed from Python 3.

Input

python3 << EOD

import vim

for window in vim.windows:
    if (window.buffer.options['buftype'] == b'terminal'):
        window.buffer.options['termwinsize'] = '10x0'

EOD

Expected Result

Success.

Actual Result

KeyError: 'termwinsize'

Is this an expected behavior or a bug?

(:set termwinsize=10x0 succeeds. The options cannot be accessed only from Python 3.)

Answer 1

It is actually the expected behavior, although that is clearly not what was intended. The key is that 'termwinsize' is "local to window", whereas 'buftype' is "local to buffer".

There is a slight --- but important --- distinction between "window" and "buffer". :h windows.txt explains this distinction in great detail. But briefly, a window is a view of a buffer.

Therefore, when accessing these options via the python interface, one would use window.options['termwinsize'], and window.buffer.options['buftype'] respectively.