## **Typer**, the FastAPI of CLIs

<a href="https://typer.tiangolo.com"><img src="https://typer.tiangolo.com/img/logo-margin/logo-margin-vector.svg" style="width: 20%;"></a>

If you are building a <abbr title="Command Line Interface">CLI</abbr> app to be used in the terminal instead of a web API, check out [**Typer**](https://typer.tiangolo.com/).

**Typer** is FastAPI's little sibling. And it's intended to be the **FastAPI of CLIs**. ⌨️ 🚀

<a href="https://typer.tiangolo.com"><img src="https://typer.tiangolo.com/img/logo-margin/logo-margin-vector.svg" style="width: 20%;"></a>

If you are building a <abbr title="Command Line Interface">CLI</abbr> app to be used in the terminal instead of a web API, check out [**Typer**](https://typer.tiangolo.com/).

**Typer** is FastAPI's little sibling. And it's intended to be the **FastAPI of CLIs**. ⌨️ 🚀

import okhttp3.internal.http2.ErrorCode
import okhttp3.internal.http2.Settings
import okio.Buffer

/** A scripted response to be replayed by the mock web server. */
public class MockResponse {
  /** Returns the HTTP response line, such as "HTTP/1.1 200 OK". */
  public val status: String

  public val code: Int
    get() {
      val statusParts = status.split(' ', limit = 3)
      require(statusParts.size >= 2) { "Unexpected status: $status" }

And there are extra tools/scripts in place to handle translations in `./scripts/docs.py`.

/// tip

You don't need to see the code in `./scripts/docs.py`, you just use it in the command line.

///

All the documentation is in Markdown format in the directory `./docs/en/`.

Many of the tutorials have blocks of code.

But, sadly, you get nothing useful:

<img src="/img/python-types/image01.png">

### Add types { #add-types }

Let's modify a single line from the previous version.

We will change exactly this fragment, the parameters of the function, from:

```Python
    first_name, last_name
```

to:

```Python
    first_name: str, last_name: str

   * actual {@code y} values of the data and the values predicted by the fit for the {@code x}
   * values (i.e. it is the square root of the mean of the squares of the vertical distances between
   * the data points and the best fit line). For this fit, this error is a fraction {@code sqrt(1 -
   * R*R)} of the population standard deviation of {@code y}, where {@code R} is the Pearson's

///

/// warning

Have in mind that the `RequestValidationError` contains the information of the file name and line where the validation error happens so that you can show it in your logs with the relevant information if you want to.

<div class="termy">

```console
$ source .venv/Scripts/activate
```

</div>

////

/// tip

每次你在這個環境中安裝一個**新的套件**時，都需要**重新啟動**這個環境。

這麼做確保了當你使用一個由這個套件安裝的**終端（<abbr title="command line interface - 命令列介面">CLI</abbr>）程式**時，你使用的是你的虛擬環境中的程式，而不是全域安裝、可能版本不同的程式。

///

## 檢查虛擬環境是否啟動 { #check-the-virtual-environment-is-active }

檢查虛擬環境是否啟動（前面的指令是否生效）。

/// tip

```console
$ source .venv/Scripts/activate
```

</div>

////

/// tip | 提示

每次你在这个环境中安装一个 **新的包** 时，都需要 **重新激活** 这个环境。

这么做确保了当你使用一个由这个包安装的 **终端（<abbr title="command line interface - 命令行界面">CLI</abbr>）程序** 时，你使用的是你的虚拟环境中的程序，而不是全局安装、可能版本不同的程序。

///

## 检查虚拟环境是否激活 { #check-the-virtual-environment-is-active }

检查虚拟环境是否激活 (前面的命令是否生效)。

/// tip | 提示

/**
 * A specification of a {@link CacheBuilder} configuration.
 *
 * <p>{@code CacheBuilderSpec} supports parsing configuration off of a string, which makes it
 * especially useful for command-line configuration of a {@code CacheBuilder}.
 *
 * <p>The string syntax is a series of comma-separated keys or key-value pairs, each corresponding
 * to a {@code CacheBuilder} method.
 *
 * <ul>