# Python 类型提示简介

**Python 3.6+ 版本**加入了对"类型提示"的支持。

这些**"类型提示"**是一种新的语法（在 Python 3.6 版本加入）用来声明一个变量的<abbr title="例如：str、int、float、bool">类型</abbr>。

通过声明变量的类型，编辑器和一些工具能给你提供更好的支持。

这只是一个关于 Python 类型提示的**快速入门 / 复习**。它仅涵盖与 **FastAPI** 一起使用所需的最少部分...实际上只有很少一点。

整个 **FastAPI** 都基于这些类型提示构建，它们带来了许多优点和好处。

但即使你不会用到 **FastAPI**，了解一下类型提示也会让你从中受益。

/// note

如果你已经精通 Python，并且了解关于类型提示的一切知识，直接跳到下一章节吧。

///

## 动机

让我们从一个简单的例子开始：

 *   int result = 1;
 *   while ((response = response.priorResponse()) != null) {
 *     result++;
 *   }
 *   return result;
 * }
 * ```
 *
 * [1]: https://tools.ietf.org/html/rfc2817
 */
fun interface Authenticator {
  /**
   * Returns a request that includes a credential to satisfy an authentication challenge in
   * [response]. Returns null if the challenge cannot be satisfied.

J'ai testé plusieurs idées dans les éditeurs Python les plus populaires : PyCharm, VS Code, les éditeurs basés sur Jedi.

D'après la dernière <a href="https://www.jetbrains.com/research/python-developers-survey-2018/#development-tools" class="external-link" target="_blank">Enquête Développeurs Python</a>, cela couvre environ 80% des utilisateurs.

}

// Compares all the bytes returned by the given readers. Any Read
// errors cause a `false` result. A string describing the error is
// also returned.
func cmpReaders(r1, r2 io.Reader) (bool, string) {
	bufLen := 32 * 1024
	b1, b2 := make([]byte, bufLen), make([]byte, bufLen)
	for i := 0; true; i++ {
		n1, e1 := io.ReadFull(r1, b1)
		n2, e2 := io.ReadFull(r2, b2)
		if n1 != n2 {

import okio.Buffer
import okio.BufferedSource
import okio.ByteString

/**
 * An [RFC 6455][rfc_6455]-compatible WebSocket frame reader.
 *
 * This class is not thread safe.
 *
 * [rfc_6455]: http://tools.ietf.org/html/rfc6455
 */
class WebSocketReader(
  private val isClient: Boolean,
  val source: BufferedSource,
  private val frameCallback: FrameCallback,
  private val perMessageDeflate: Boolean,

Das Hinzufügen eines `\f` (ein maskiertes „Form Feed“-Zeichen) führt dazu, dass **FastAPI** die für OpenAPI verwendete Ausgabe an dieser Stelle abschneidet.

Sie wird nicht in der Dokumentation angezeigt, aber andere Tools (z. B. Sphinx) können den Rest verwenden.

```Python hl_lines="19-29"
{!../../docs_src/path_operation_advanced_configuration/tutorial004.py!}
```

## Zusätzliche Responses

   * <p><b>Performance note:</b> When feasible, {@code initialCapacity} should be the exact number
   * of values that will be added, if that knowledge is readily available. It is better to guess a
   * value slightly too high than slightly too low. If the value is not exact, the {@link
   * ImmutableDoubleArray} that is built will very likely occupy more memory than strictly
   * necessary; to trim memory usage, build using {@code builder.build().trimmed()}.

			// the parser is more liberal than what USTAR actually permits.
			notASCII := func(r rune) bool { return r >= 0x80 }
			if bytes.IndexFunc(tr.blk[:], notASCII) >= 0 {
				hdr.Format = FormatUnknown // Non-ASCII characters in block.
			}
			nul := func(b []byte) bool { return int(b[len(b)-1]) == 0 }
			if !(nul(v7.size()) && nul(v7.mode()) && nul(v7.uid()) && nul(v7.gid()) &&

        if (firstTimeSeeingThisException) {
          log(throwable);
          return;
        }
      }
    }

    /*
     * TODO(cpovirk): Should whenAllComplete().call*() log errors, too? Currently, it doesn't call
     * handleException() at all.
     */
    if (throwable instanceof Error) {
      /*
       * TODO(cpovirk): Do we really want to log this if we called setException(throwable) and it

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):