#### Operation { #operation }

"Operation" here refers to one of the HTTP "methods".

One of:

* `POST`
* `GET`
* `PUT`
* `DELETE`

...and the more exotic ones:

* `OPTIONS`
* `HEAD`
* `PATCH`
* `TRACE`

In the HTTP protocol, you can communicate to each path using one (or more) of these "methods".

---

    * JSON objects (`dict`).
    * JSON array (`list`) defining item types.
    * String (`str`) fields, defining min and max lengths.
    * Numbers (`int`, `float`) with min and max values, etc.

* Validation for more exotic types, like:
    * URL.
    * Email.
    * UUID.
    * ...and others.

All the validation is handled by the well-established and robust **Pydantic**.

///

If you are using `pip` to install packages (it comes by default with Python), you should **upgrade** it to the latest version.

Many exotic errors while installing a package are solved by just upgrading `pip` first.

/// tip

You would normally do this **once**, right after you create the virtual environment.

///

Python runtime only and makes it possible to reload Python objects identical to the saved originals. The format supports non-numerical state such as vocabulary files and lookup tables, and it is easy to customize in the case of custom layers with exotic elements of state (e.g. a FIFOQueue). The format does not rely on bytecode or pickling, and is safe by default. Note that as a result, Python `lambdas` are disallowed at loading time. If you want to use `lambdas`, you can pass `safe_mode=False` to...

* Update "new issue" templates. PR [#749](https://github.com/tiangolo/fastapi/pull/749).
* Fix serialization of errors for exotic Pydantic types. PR [#748](https://github.com/tiangolo/fastapi/pull/748) by [@dmontagu](https://github.com/dmontagu).

## 0.44.0