from typing import Optional

app = FastAPI()


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


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


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


@app.put("/items/{item_id}")

///

/// check

Bei der Einbindung von Routern müssen Sie sich keine Gedanken über die Performanz machen.

Dies dauert Mikrosekunden und geschieht nur beim Start.

Es hat also keinen Einfluss auf die Leistung. ⚡

///

### Einen `APIRouter` mit benutzerdefinierten `prefix`, `tags`, `responses` und `dependencies` einfügen

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

      for (N node : graph.nodes()) {
        if (!visitedNodes.contains(node)) {
          Set<N> reachableNodes = reachableNodes(graph, node);
          visitedNodes.addAll(reachableNodes);
          int pairwiseMatch = 1; // start at 1 to include self-loops
          for (N nodeU : reachableNodes) {
            for (N nodeV : Iterables.limit(reachableNodes, pairwiseMatch++)) {
              transitiveClosure.putEdge(nodeU, nodeV);
            }

[kubernetes-client-linux-amd64.tar.gz](https://storage.googleapis.com/kubernetes-release/release/v1.2.7/kubernetes-client-linux-amd64.tar.gz) | `9a5fcd87514b88eb25173e574aef5b5343816c07ab5947d06787c9f12c40f54a`

// in 'pool.bin', this is eventually used for decommissioning the pool.
func (z *erasureServerPools) Init(ctx context.Context) error {
	// Load rebalance metadata if present
	if err := z.loadRebalanceMeta(ctx); err == nil {
		// Start rebalance routine if we can reload rebalance metadata.
		z.StartRebalance()
	}

	meta := poolMeta{}
	if err := meta.load(ctx, z.serverPools[0], z.serverPools); err != nil {
		return err
	}

          return null;
        }
      }
      return null;
    }

    @Override
    Iterator<Entry<Cut<C>, Range<C>>> entryIterator() {
      /*
       * We want to start the iteration at the first range where the upper bound is in
       * upperBoundWindow.
       */
      Iterator<Range<C>> backingItr;
      if (!upperBoundWindow.hasLowerBound()) {

  // value. In our example, it would be another entry for a key whose short hash is also 0x6f.
  //
  // Essentially, then, `table[h]` gives us the start of a linked list in `entries`, where every
  // element of the list has the short hash value h.
  //
  // A wrinkle here is that the value 0 (called UNSET in the code) is used as the equivalent of a

    }

    static String unescape(String str) throws NumberFormatException, UnsupportedEncodingException {
        char ch;
        int i, j, state, len;
        char[] out;
        byte[] b = new byte[1];

        if (str == null) {
            return null;
        }

        len = str.length();
        out = new char[len];
        state = 0;

}

func writeAllMetadataWithRevert(ctx context.Context, disks []StorageAPI, origbucket, bucket, prefix string, files []FileInfo, quorum int, revert bool) ([]StorageAPI, error) {
	g := errgroup.WithNErrs(len(disks))

	// Start writing `xl.meta` to all disks in parallel.
	for index := range disks {
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			// Pick one FileInfo for a disk at index.