Pydantic中Optional 和Union类型的使用

from typing import Optional
from pydantic import BaseModel

class User(BaseModel):
    id: int
    name: str
    age: Optional[int] = None  # age 可以是 int 或 None

user1 = User(id=1, name='Alice', age=30)
user2 = User(id=2, name='Bob')  # age 省略，默认为 None

print(user1)
print(user2)

from pydantic import ValidationError

try:
    user = User(id=3, name='Charlie', age='thirty')
except ValidationError as e:
    print(e)

from typing import Union
from pydantic import BaseModel

class Item(BaseModel):
    id: int
    value: Union[str, int]  # value 可以是 str 或 int

item1 = Item(id=1, value='a string')
item2 = Item(id=2, value=100)

print(item1)
print(item2)

from pydantic import ValidationError

try:
    item = Item(id=3, value=[1, 2, 3])  # list 不是合法的类型
except ValidationError as e:
    print(e)

class Product(BaseModel):
    id: int
    discount: Optional[Union[int, float]] = None  # discount 可以是 int、float 或 None

product1 = Product(id=1, discount=20)
product2 = Product(id=2, discount=15.5)
product3 = Product(id=3)  # discount 省略，默认为 None

print(product1)
print(product2)
print(product3)

from pydantic import ValidationError

try:
    product = Product(id=4, discount='50%')  # str 不是合法的类型
except ValidationError as e:
    print(e)