* A special case is `204`, "No Content".  This response is used when there is no content to return to the client, and so the response must not have a body.
* **`300 - 399`** are for "Redirection".  Responses with these status codes may or may not have a body, except for `304`, "Not Modified", which must not have one.
* **`400 - 499`** are for "Client error" responses. These are the second type you would probably use the most.

You can use `SecurityScopes` at any point, and in multiple places, it doesn't have to be at the "root" dependency.

It will always have the security scopes declared in the current `Security` dependencies and all the dependants for **that specific** *path operation* and **that specific** dependency tree.

Now, from a **developer's perspective**, here are several things to keep in mind while thinking about HTTPS:

* For HTTPS, **the server** needs to **have "certificates"** generated by a **third party**.
    * Those certificates are actually **acquired** from the third party, not "generated".
* Certificates have a **lifetime**.
    * They **expire**.
    * And then they need to be **renewed**, **acquired again** from the third party.

	if sepIndex == -1 {
		return nil, fmt.Errorf("'%s' does not have a valid range value", rangeString)
	}

	offsetBeginString := byteRangeString[:sepIndex]
	offsetBegin := int64(-1)
	// Convert offsetBeginString only if its not empty.
	if len(offsetBeginString) > 0 {
		if offsetBeginString[0] == '+' {
			return nil, fmt.Errorf("Byte position ('%s') must not have a sign", offsetBeginString)

     *
     * <p>This will be called at most once after all the services have entered the {@linkplain
     * State#RUNNING running} state. If any services fail during start up or {@linkplain
     * State#FAILED fail}/{@linkplain State#TERMINATED terminate} before all other services have
     * started {@linkplain State#RUNNING running} then this method will not be called.
     */

To see all the options you have, checkout <a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">Pydantic's Type Overview</a>. You will see some examples in the next chapter.

For example, as in the `Image` model we have a `url` field, we can declare it to be an instance of Pydantic's `HttpUrl` instead of a `str`:

# Security - First Steps { #security-first-steps }

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

But you still need to use `Path` for the `item_id` path parameter. And you don't want to use `Annotated` for some reason.

Python will complain if you put a value with a "default" before a value that doesn't have a "default".

But you can re-order them, and have the value without a default (the query parameter `q`) first.

What inspired **FastAPI**, how it compares to alternatives and what it learned from them.

## Intro { #intro }

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

I have been avoiding the creation of a new framework for several years. First I tried to solve all the features covered by **FastAPI** using many different frameworks, plug-ins, and tools.

* **Uvicorn**:
    * Will have the best performance, as it doesn't have much extra code apart from the server itself.