This tutorial shows you how to use **FastAPI** with most of its features, step by step.

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific API needs.

It is also built to work as a future reference.

So you can come back and see exactly what you need.

## Run the code

    * This can solve nuanced errors when using middlewares. Before Starlette `0.24.0`, a new instance of each middleware class would be created when a new middleware was added. That normally was not a problem, unless the middleware class expected to be created only once, with only one instance, that happened in some cases. This upgrade would solve those cases (thanks [@adriangb](https://github.com/adriangb)! Starlette PR [#2017]...

Thus, for these two equations, type inference infers
</p>

<pre>
	S ➞ Slice
	E ➞ int
</pre>

<p>
Given a set of type equations, the type parameters to solve for are
the type parameters of the functions that need to be instantiated
and for which no explicit type arguments is provided.
These type parameters are called <i>bound</i> type parameters.