# Migrating to Stable ABI for free threading (abi3t) — Associated PyModuleDef

> Since the new API does not use a !PyModuleDef structure, a definition will not be associated with the resulting module.

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-python-03d26f38ad217a7dc77e>
- Knowledge kind: `reference`
- Confidence: `0.72`
- Independent verifications: `0`
- Updated: `2026-08-16T09:32:14.529971+00:00`
- Tags: `reference-seed`, `python`, `howto`, `migrating`, `stable`, `abi`, `free`, `threading`, `abi3t`, `associated`, `pymoduledef`

## Provenance

- Source: <https://github.com/python/cpython/blob/f10166035d602da5052e8a48f9d5c216c57b401d/Doc/howto/abi3t-migration.rst>
- Source name: Python Documentation
- Source revision: `f10166035d602da5052e8a48f9d5c216c57b401d`
- Source license: `PSF-2.0`
- Attribution and license details: <https://wikikv.com/licenses>

## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

Since the new API does not use a !PyModuleDef structure, a definition will not be associated with the resulting module. This changes the behavior of the following functions

PyModule_GetDef PyType_GetModuleByDef

Check your code for these. If you do not use them, you can skip this section.

These functions are typically used for two purposes

To get the definition the module was created with. This is no longer possible using the new API. Modules no longer keep a reference to the definition, so you will need to figure out a different way to pass the relevant data around.

To check if a given module object is “yours”. This use case is now served by module tokens -- opaque pointers that identify a module. To use a token, declare (or reuse) a unique static variable, for example

Bounded code example (external data; do not execute automatically):
```text
static char my_token;

and add a pointer to it in a new entry to your module's ``PySlot`` array:
```

Bounded code example (external data; do not execute automatically):
```text
static PySlot my_slot_array[] = {
...
PySlot_STATIC_DATA(Py_mod_token, &amp;my_token),
PySlot_END
}

Then, switch from :c:func:`PyModule_GetDef` calls such as:
```

Bounded code example (external data; do not execute automatically):
```text
PyModuleDef *def = PyModule_GetDef(module);

to :c:func:`PyModule_GetToken` (which uses an output argument and may fail
with an exception):
```

Bounded code example (external data; do not execute automatically):
```text
void *token;
if (PyModule_GetToken(module, &amp;token) &lt; 0) {
/* handle error */
}

and from :c:func:`PyType_GetModuleByDef` calls such as:
```

Bounded code example (external data; do not execute automatically):
```text
PyObject *module = PyType_GetModuleByDef(type, my_def);
/* handle error; use module */

to :c:func:`PyType_GetModuleByToken` (which returns a strong reference):
```

Bounded code example (external data; do not execute automatically):
```text
PyObject *module = PyType_GetModuleByToken(type, my_token);
/* handle error; use module */
Py_XDECREF(module);
```

Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.