mirror of
https://github.com/kennethreitz/pydantic.git
synced 2026-06-05 23:00:18 +00:00
Samuel Colvin
33b7d52d31
* moving docs to mkdocs * transfering readme to md and more * fixing build * splitting usage.md * improving schema.md and index.md * fix make_history.rst * models intro * working on data conversation and required fields * more fixes to models.md * list all standard types supported * list of pydantic types * tweaks * update links in code * Apply suggestions from code review incorporate @dmontagu's suggestions. Co-Authored-By: dmontagu <35119617+dmontagu@users.noreply.github.com> * Apply suggestions from code review more missed suggestions. Co-Authored-By: dmontagu <35119617+dmontagu@users.noreply.github.com> * Apply suggestions from code review more corrects. * cleanup * Field order warning * fix and regenerate benchmarks * format examples better, cleanup * improve schema mapping table * correct highlighting file types in schema.md * add redirects in javascript * add logo
68 lines
2.3 KiB
Markdown
68 lines
2.3 KiB
Markdown
!!! note
|
|
Both postponed annotations via the future import and `ForwardRef` require python 3.7+.
|
|
|
|
Postponed annotations (as described in [PEP563](https://www.python.org/dev/peps/pep-0563/))
|
|
"just work".
|
|
|
|
```py
|
|
{!./examples/postponed_annotations.py!}
|
|
```
|
|
_(This script is complete, it should run "as is")_
|
|
|
|
Internally *pydantic* will call a method similar to `typing.get_type_hints` to resolve annotations.
|
|
|
|
In cases where the referenced type is not yet defined, `ForwardRef` can be used (although referencing the
|
|
type directly or by its string is a simpler solution in the case of
|
|
[self-referencing models](#self-referencing-models)).
|
|
|
|
You may need to call `Model.update_forward_refs()` after creating the model,
|
|
this is because in the example below `Foo` doesn't exist before it has been created (obviously) so `ForwardRef`
|
|
can't initially be resolved. You have to wait until after `Foo` is created, then call `update_forward_refs`
|
|
to properly set types before the model can be used.
|
|
|
|
```py
|
|
{!./examples/forward_ref.py!}
|
|
```
|
|
_(This script is complete, it should run "as is")_
|
|
|
|
!!! warning
|
|
To resolve strings (type names) into annotations (types) *pydantic* needs a dict to lookup,
|
|
for this it uses `module.__dict__` just as `get_type_hints` does. That means *pydantic* does not play well
|
|
with types not defined in the global scope of a module.
|
|
|
|
For example, this works fine:
|
|
|
|
```py
|
|
{!./examples/postponed_works.py!}
|
|
```
|
|
|
|
While this will break:
|
|
|
|
```py
|
|
{!./examples/postponed_broken.py!}
|
|
```
|
|
|
|
Resolving this is beyond the call for *pydantic*: either remove the future import or declare the types globally.
|
|
|
|
## Self-referencing Models
|
|
|
|
Data structures with self-referencing models are also supported, provided the function
|
|
`update_forward_refs()` is called once the model is created (you will be reminded
|
|
with a friendly error message if you don't).
|
|
|
|
Within the model, you can refer to the not-yet-constructed model by a string :
|
|
|
|
```py
|
|
{!./examples/self_referencing_string.py!}
|
|
```
|
|
_(This script is complete, it should run "as is")_
|
|
|
|
Since `python 3.7`, You can also refer it by its type, provided you import `annotations` (see
|
|
[above](postponed_annotations.md) for support depending on Python
|
|
and pydantic versions).
|
|
|
|
```py
|
|
{!./examples/self_referencing_annotations.py!}
|
|
```
|
|
_(This script is complete, it should run "as is")_
|