print(f"Hello {name} from Python")
```

/// tip

The second argument to [`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) is the default value to return.

If not provided, it's `None` by default, here we provide `"World"` as the default value to use.

///

Then you could call that Python program:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float = 10.5
    tags: list[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The bartenders", "price": 62, "tax": 20.2},
    "baz": {"name": "Baz", "description": None, "price": 50.2, "tax": 10.5, "tags": []},
}

 */
@Experimental
@Immutable
public enum DependencyScope {

    /**
     * None. Allows you to declare dependencies (for example to alter reactor build order) but in reality dependencies
     * in this scope are not part of any path scope.
     */
    NONE("none", false),

    /**
     * Undefined. When no scope is explicitly given, UNDEFINED will be used, but its meaning will depend on

from pydantic.v1 import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(user_agent: str | None = Header(default=None)):

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: list[str] | None = Query(default=None)):
    query_items = {"q": q}

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(x_token: list[str] | None = Header(default=None)):

from typing import Annotated

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: Annotated[str | None, Header(convert_underscores=False)] = None,
):

]


@app.get("/items/stream", response_class=EventSourceResponse)
async def stream_items(
    last_event_id: Annotated[int | None, Header()] = None,
) -> AsyncIterable[ServerSentEvent]:
    start = last_event_id + 1 if last_event_id is not None else 0
    for i, item in enumerate(items):
        if i < start:
            continue

		expectedCode      int
	}{
		// If-None-Match(false) and If-Modified-Since(true)
		{
			name:            "If-None-Match1",
			ifNoneMatch:     "aa",
			ifModifiedSince: "Sun, 26 Aug 2024 02:01:00 GMT",
			objInfo:         objInfo,
			expectedFlag:    true,
			expectedCode:    304,
		},
		// If-Modified-Since(false)
		{
			name:            "If-None-Match2",
			ifNoneMatch:     "aaa",