Clarification around usage of Union by somada141 · Pull Request #594 · pydantic/pydantic

somada141 · 2019-06-14T07:57:08Z

Change Summary

Adds examples of the incorrect and correct usage of Union when defining type annotations with multiple types and updated documentation. This is discussed further under #514

Checklist

Unit tests for the changes exist
Tests pass on CI and coverage remains at 100%
Documentation reflects the changes where applicable
HISTORY.rst has been updated
- if this is the first change since a release, please add a new section
- include the issue number or this pull request number #<number>
- include your github username @<whomever>

… in type annotations.

codecov · 2019-06-14T14:12:11Z

Codecov Report

Merging #594 into master will decrease coverage by 2.71%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #594      +/-   ##
==========================================
- Coverage     100%   97.28%   -2.72%     
==========================================
  Files          15       15              
  Lines        2542     2542              
  Branches      504      504              
==========================================
- Hits         2542     2473      -69     
- Misses          0       58      +58     
- Partials        0       11      +11

somada141 · 2019-06-14T14:27:56Z

@samuelcolvin please have a look when you get a chance

samuelcolvin

Can you also add an entry to HISTORY.rst, I know this isn't a code change but it's still useful in the changelog and it gets your name into contributors.

samuelcolvin · 2019-06-14T15:50:26Z

+
+(This script is complete, it should run "as is")
+
+However, as can be seen above, *pydantic* will attempt to 'match' any of the models (classes) defined under ``Union`` and will use the first one that matches. In the above example the ``id`` of ``user_03`` was defined as a ``uuid.UUID`` class (which is defined under the attribute's ``Union`` annotation) but as the ``uuid.UUID`` can be marshalled into an ``int`` it chose to match against the ``int`` type and disregarded the other types.


please hard wrap this text.

Also models (classes) can changed to types.

samuelcolvin · 2019-06-14T15:50:31Z

+
+However, as can be seen above, *pydantic* will attempt to 'match' any of the models (classes) defined under ``Union`` and will use the first one that matches. In the above example the ``id`` of ``user_03`` was defined as a ``uuid.UUID`` class (which is defined under the attribute's ``Union`` annotation) but as the ``uuid.UUID`` can be marshalled into an ``int`` it chose to match against the ``int`` type and disregarded the other types.
+
+As such, it is recommended that when defining ``Union`` annotations that the most specific model (class) is defined first and followed by less specific models (classes). In the above example, the ``UUID`` class should precede the ``int`` and ``str`` classes to preclude the unexpected representation as such:


samuelcolvin · 2019-06-14T15:52:36Z

 * **django-restful-framework** ``v3.9.4``


+Usage of ``Union`` in Annotations and Type Order


can you move this above benchmarks.

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

…ada141/pydantic into fix/add_union_gotcha_to_doco

somada141 · 2019-06-14T22:44:41Z

@samuelcolvin I updated HISTORY.rst but didn't set a version for the release, does the way I added to it make sense?

Add support for InitVar (pydantic#591)

…a_to_doco # Conflicts: # HISTORY.rst

somada141 · 2019-06-14T22:50:00Z

nvm realised you pushed a new version on it. updated

samuelcolvin

otherwise fine.

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

somada141 · 2019-06-15T12:06:20Z

@samuelcolvin updated

samuelcolvin · 2019-06-15T13:06:14Z

merged, thanks so much.

Docs will be updated on the next release.

somada141 · 2019-06-15T13:24:43Z

beautiful thanks a lot for the help @samuelcolvin

somada141 added 3 commits June 14, 2019 17:23

Added two code examples on the correct and incorrect usage of Union…

dd84cf9

… in type annotations.

Updated documentation.

4403bee

reST fix.

bc8f95f

samuelcolvin reviewed Jun 14, 2019

View reviewed changes

somada141 and others added 7 commits June 15, 2019 08:06

Update docs/examples/union_type_incorrect.py

6266d51

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update docs/examples/union_type_incorrect.py

ea65e4d

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update docs/examples/union_type_incorrect.py

e72d4c7

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update docs/examples/union_type_correct.py

8aecb68

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

PR comments.

5c84ef8

Merge branch 'fix/add_union_gotcha_to_doco' of https://github.com/som…

7b45ac6

…ada141/pydantic into fix/add_union_gotcha_to_doco

Updated HISTORY.rst.

157e128

somada141 and others added 2 commits June 15, 2019 08:18

Merge pull request #1 from samuelcolvin/master

0f76f9d

Add support for InitVar (pydantic#591)

Merge remote-tracking branch 'origin/master' into fix/add_union_gotch…

db413d2

…a_to_doco # Conflicts: # HISTORY.rst

samuelcolvin reviewed Jun 15, 2019

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Comment thread HISTORY.rst Outdated

Comment thread docs/index.rst Outdated

Comment thread docs/index.rst Outdated

Comment thread docs/index.rst

somada141 and others added 4 commits June 15, 2019 21:34

Update docs/index.rst

9211d6a

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update HISTORY.rst

c69b062

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update docs/index.rst

84ab94c

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

Update docs/index.rst

30a5e54

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

samuelcolvin merged commit 84820bd into pydantic:master Jun 15, 2019

alexdrydew pushed a commit to alexdrydew/pydantic that referenced this pull request Dec 23, 2023

Remove warning for mutable default (pydantic#594)

493643e


		(This script is complete, it should run "as is")

		However, as can be seen above, pydantic will attempt to 'match' any of the models (classes) defined under ``Union`` and will use the first one that matches. In the above example the ``id`` of ``user_03`` was defined as a ``uuid.UUID`` class (which is defined under the attribute's ``Union`` annotation) but as the ``uuid.UUID`` can be marshalled into an ``int`` it chose to match against the ``int`` type and disregarded the other types.


		However, as can be seen above, pydantic will attempt to 'match' any of the models (classes) defined under ``Union`` and will use the first one that matches. In the above example the ``id`` of ``user_03`` was defined as a ``uuid.UUID`` class (which is defined under the attribute's ``Union`` annotation) but as the ``uuid.UUID`` can be marshalled into an ``int`` it chose to match against the ``int`` type and disregarded the other types.

		As such, it is recommended that when defining ``Union`` annotations that the most specific model (class) is defined first and followed by less specific models (classes). In the above example, the ``UUID`` class should precede the ``int`` and ``str`` classes to preclude the unexpected representation as such:

		* django-restful-framework ``v3.9.4``


		Usage of ``Union`` in Annotations and Type Order

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somada141 commented Jun 14, 2019 •

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