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98 lines
2.6 KiB
Markdown
98 lines
2.6 KiB
Markdown
# Read One Model with FastAPI
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Let's now add a *path operation* to read a single model to our **FastAPI** application.
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## Path Operation for One Hero
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Let's add a new *path operation* to read one single hero.
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We want to get the hero based on the `id`, so we will use a **path parameter** `hero_id`.
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!!! info
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If you need to refresh how *path parameters* work, including their data validation, check the <a href="https://fastapi.tiangolo.com/tutorial/path-params/" class="external-link" target="_blank">FastAPI docs about Path Parameters</a>.
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```Python hl_lines="8"
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:1-4]!}
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# Code here omitted 👈
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:61-67]!}
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```
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<details>
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<summary>👀 Full file preview</summary>
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```Python
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py!}
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```
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</details>
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For example, to get the hero with ID `2` we would send a `GET` request to:
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```
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/heroes/2
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```
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## Handling Errors
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Then, because FastAPI already takes care of making sure that the `hero_id` is an actual integer, we can use it directly with `Hero.get()` to try and get one hero by that ID.
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But if the integer is not the ID of any hero in the database, it will not find anything, and the variable `hero` will be `None`.
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So, we check it in an `if` block, if it's `None`, we raise an `HTTPException` with a `404` status code.
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And to use it, we first import `HTTPException` from `fastapi`.
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This will let the client know that they probably made a mistake on their side and requested a hero that doesn't exist in the database.
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```Python hl_lines="3 11-13"
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:1-4]!}
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# Code here omitted 👈
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:61-67]!}
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```
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<details>
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<summary>👀 Full file preview</summary>
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```Python
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py!}
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```
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</details>
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## Return the Hero
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Then, if the hero exists, we return it.
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And because we are using the `response_model` with `HeroRead`, it will be validated, documented, etc.
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```Python hl_lines="8 14"
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:1-4]!}
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# Code here omitted 👈
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py[ln:61-67]!}
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```
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<details>
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<summary>👀 Full file preview</summary>
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```Python
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{!./docs_src/tutorial/fastapi/read_one/tutorial001.py!}
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```
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</details>
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## Check the Docs UI
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We can then go to the docs UI and see the new *path operation*.
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<img class="shadow" alt="Interactive API docs UI" src="/img/tutorial/fastapi/read-one/image01.png">
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## Recap
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You can combine **FastAPI** features like automatic path parameter validation to get models by ID.
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