## Execution of dependencies with `yield`

The sequence of execution is more or less like this diagram. Time flows from top to bottom. And each column is one of the parts interacting or executing code.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield

    title: JWT Authentication with FastAPI and AWS Cognito
  - author: Ankush Thakur
    author_link: https://geekflare.com/author/ankush/
    link: https://geekflare.com/python-asynchronous-web-frameworks/
    title: Top 5 Asynchronous Web Frameworks for Python
  - author: Nico Axtmann
    author_link: https://www.linkedin.com/in/nico-axtmann

```Python
def get_settings():
    return Settings()
```

we would create that object for each request, and we would be reading the `.env` file for each request. ⚠️

But as we are using the `@lru_cache` decorator on top, the `Settings` object will be created only once, the first time it's called. ✔️

=== "Python 3.9+"

    ```Python hl_lines="1  11"
    {!> ../../../docs_src/settings/app03_an_py39/main.py!}
    ```

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```Dockerfile
COPY ./requirements.txt /code/requirements.txt
```

Docker and other tools **build** these container images **incrementally**, adding **one layer on top of the other**, starting from the top of the `Dockerfile` and adding any files created by each of the instructions of the `Dockerfile`.

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