GeezerVison

All modules created using multi-phase initialization are expected to support
:ref:`sub-interpreters <sub-interpreter-support>` and multiple
:c:func:`Py_Initialize`/:c:func:`Py_Finalize` cycles correctly.
Typically, extensions ensure this in one of these ways:

Modules created using multi-phase initialization are expected to handle
sub-interpreters in either of the following two ways:

* either they fully support multiple interpreters by
  :ref:`isolating module instances <isolating-extensions-howto>`;
* or they signal that multiple interpreters are not supported by
  :ref:`raising an error on repeated initialization <isolating-extensions-optout>`
  and/or limiting a module to the main interpreter using
  :c:data:`Py_mod_multiple_interpreters`.

This way, users will not encounter crashes or undefined behavior when
trying to use these modules from multiple interpreters.

Multi-phase initialization allows creating multiple independent instances of the
module object.
Extensions are expected to handle this in one of the following ways:

* either by :ref:`isolating module instances <isolating-extensions-howto>`;
* and/or by :ref:`raising an error on repeated initialization <isolating-extensions-optout>`;
* and/or limiting a module to the main interpreter using
  :c:data:`Py_mod_multiple_interpreters`.

This way, users will not encounter crashes or undefined behavior when
trying to use these modules from :ref:`sub-interpreters <sub-interpreter-support>`.
The first two ways also prevent crashes when reusing the module after
Python runtime reinitialization (:c:func:`Py_Finalize` and :c:func:`Py_Initialize`)
and reimporting a module after it is removed from :py:attr:`sys.modules`.

When using per-module state, module instances should be :ref:`isolated
<isolating-extensions-howto>` to ensure that they are free of unwanted
side-effects. If the module still uses global state, or it otherwise has not
yet been isolated, either or both of of the following two options should be used:

* :ref:`raising an error on repeated initialization <isolating-extensions-optout>`
* limiting a module to the main interpreter using
  :c:data:`Py_mod_multiple_interpreters`.

This way, users will not encounter crashes or undefined behavior when
trying to use these modules from :ref:`sub-interpreters <sub-interpreter-support>`.
Ensuring a module is properly isolated or raising an explicit error also prevent
crashes when reusing the module after Python runtime reinitialization
(:c:func:`Py_Finalize` and :c:func:`Py_Initialize`) or reimporting a module after
it has been removed from :py:attr:`sys.modules`.

When using per-module state, module instances should be :ref:`isolated
<isolating-extensions-howto>` to ensure that they are free of unwanted
side-effects. If the module still uses global state, or it otherwise has not
yet been isolated, either or both of of the following two options should be used:

* :ref:`raising an error on repeated initialization <isolating-extensions-optout>`
* limiting a module to the main interpreter using
  :c:data:`Py_mod_multiple_interpreters`.

This way, users will not encounter crashes or undefined behavior when
trying to use these modules from :ref:`sub-interpreters <sub-interpreter-support>`.
Ensuring a module is properly isolated or raising an explicit error also prevent
crashes when reusing the module after Python runtime reinitialization
(:c:func:`Py_Finalize` and :c:func:`Py_Initialize`) or reimporting a module after
it has been removed from :py:attr:`sys.modules`.