# Learn { #learn }

Here are the introductory sections and the tutorials to learn **FastAPI**.

///

## Learn More { #learn-more }

You can learn more about **GraphQL** in the <a href="https://graphql.org/" class="external-link" target="_blank">official GraphQL documentation</a>.

          docstring_section_style: spacy
          signature_crossrefs: true
          show_symbol_type_heading: true
          show_symbol_type_toc: true
nav:
- FastAPI: index.md
- features.md
- Learn:
  - learn/index.md
  - python-types.md
  - async.md
  - environment-variables.md
  - virtual-environments.md
  - Tutorial - User Guide:
    - tutorial/index.md
    - tutorial/first-steps.md

# Security Policy

Security is very important for FastAPI and its community. 🔒

Learn more about it below. 👇

## Versions

The latest version of FastAPI is supported.

You are encouraged to [write tests](https://fastapi.tiangolo.com/tutorial/testing/) for your application and update your FastAPI version frequently after ensuring that your tests are passing. This way you will benefit from the latest features, bug fixes, and **security fixes**.

ups-of-path-operations }

Later, when reading about how to structure bigger applications ([Bigger Applications - Multiple Files](../../tutorial/bigger-applications.md){.internal-link target=_blank}), possibly with multiple files, you will learn how to declare a single `dependencies` parameter for a group of *path operations*....

Check the in-code annotation tips above to see more specific details.

## Learn More { #learn-more }

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.

To learn more, check the <a href="https://docs.pydantic.dev/latest/concepts/dataclasses/" class="external-link" target="_blank">Pydantic docs about dataclasses</a>.

If something seems interesting and useful to your project, go ahead and check it, but otherwise, you might probably just skip them.

/// tip

If you want to **learn FastAPI** in a structured way (recommended), go and read the [Tutorial - User Guide](../tutorial/index.md){.internal-link target=_blank} chapter by chapter instead.

onous-web-frameworks/ title: Top 5 Asynchronous Web Frameworks for Python - author: Nico Axtmann author_link: https://www.linkedin.com/in/nico-axtmann link: https://medium.com/@nico.axtmann95/deploying-a-scikit-learn-model-with-onnx-und-fastapi-1af398268915 title: Deploying a scikit-learn model with ONNX and FastAPI - author: Nils de Bruin author_link: https://medium.com/@nilsdebruin link: https://medium.com/data-rebels/fastapi-authentication-revisited-enabling-api-key-authentication-122dc5975680...

*   [TensorFlow Codelabs](https://codelabs.developers.google.com/?cat=TensorFlow)
*   [TensorFlow Blog](https://blog.tensorflow.org)
*   [Learn ML with TensorFlow](https://www.tensorflow.org/resources/learn-ml)
*   [TensorFlow Twitter](https://twitter.com/tensorflow)
*   [TensorFlow YouTube](https://www.youtube.com/channel/UC0rqucBdTuFTjJiefW5t-IQ)

 */
package okhttp3.internal.connection

import okhttp3.Route

/**
 * A denylist of failed routes to avoid when creating a new connection to a target address. This is
 * used so that OkHttp can learn from its mistakes: if there was a failure attempting to connect to
 * a specific IP address or proxy server, that failure is remembered and alternate routes are
 * preferred.
 */
class RouteDatabase {