Garbage collection is the big problem.  It is fine for the Go world to
have pointers into the C world and to free those pointers when they
are no longer needed.  To help, the Go code can define Go objects
holding the C pointers and use runtime.SetFinalizer on those Go objects.

It is much more difficult for the C world to have pointers into the Go
world, because the Go garbage collector is unaware of the memory

ate":"CA","PlateExpiry":"201503","Make":"NISS","BodyStyle":"PA","Color":"BK","Location":"200 WORLD WAY","Route":"2R2","Agency":2,"ViolationCode":"8939","ViolationDescr":"WHITE CURB","Fine":58,"Latitude":6439997.9,"Longitude":1802686.4} {"Ticket":1104820732,"IssueData":"2015-12-26T00:00:00","IssueTime":"1515","RPState":"CA","PlateExpiry":"","Make":"ACUR","BodyStyle":"PA","Color":"WH","Location":"100 WORLD WAY","Route":"2F11","Agency":2,"ViolationCode":"000","ViolationDescr":"17104h","Fine":"","La...

                .collect(Collectors.toSet());
    }

    private ClassRealm newRealm(String id) {
        synchronized (world) {
            String realmId = id;

            Random random = new Random();

            while (true) {
                try {
                    ClassRealm classRealm = world.newRealm(realmId, null);

                    logger.debug("Created new class realm {}", realmId);

{"text": "hello world\\n2nd line"}...

      placeholder: |
        from fastapi import FastAPI

        app = FastAPI()


        @app.get("/")
        def read_root():
            return {"Hello": "World"}
      render: python
    validations:
      required: true
  - type: textarea
    id: description
    attributes:
      label: Description
      description: |
        What is the problem, question, or error?

例如，你可以建立一個名為 `main.py` 的檔案，其中包含以下內容：

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

第二個參數是 <a href="https://docs.python.org/zh-tw/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的預設回傳值。

如果沒有提供，預設值為 `None`，這裡我們提供 `"World"` 作為預設值。

///

然後你可以呼叫這個 Python 程式：

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

from docs_src.behind_a_proxy.tutorial004_py39 import app

client = TestClient(app)


def test_main():
    response = client.get("/app")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200
    assert response.json() == snapshot(
        {

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_main():

def say_hi(name: str | None = None):
    if name is not None:
        print(f"Hey {name}!")
    else:

hello world dir/bar foo readonly important...