What is the typing.Required and NotRequired?

Question

Accepted Answer

**Required** marks TypedDict keys as **mandatory**. **NotRequired** makes them **optional**.

```python
from typing import TypedDict, Required, NotRequired

# Default: all required
class User(TypedDict):
    name: str
    email: str
    age: int

# With total=False: all optional
class UserOptional(TypedDict, total=False):
    name: str
    email: str

# Mixed: some required, some optional
class UserMixed(TypedDict):
    name: Required[str]
    email: Required[str]
    age: NotRequired[int]
    bio: NotRequired[str]

# Usage
user: UserMixed = {"name": "Alice", "email": "alice@example.com"}  # OK
user: UserMixed = {"name": "Alice", "email": "a@b.com", "age": 25}  # OK
# user: UserMixed = {"name": "Alice"}  # Error: email is Required

# With FastAPI
from fastapi import FastAPI

app = FastAPI()

class CreateUserRequest(TypedDict):
    name: Required[str]
    email: Required[str]
    age: NotRequired[int]
    bio: NotRequired[str]

@app.post("/users/")
async def create_user(user: CreateUserRequest):
    return user
```

**Benefits:**
- Fine-grained control.
- Clear API contracts.
- Better documentation.

Python: What is the typing.Required and NotRequired?