Update 'README.md'

README.md

@@ -1,2 +1,38 @@
 # pydantic
 
+数据验证和设置管理库,
+
+```
+pip install pydantic
+
+```
+
+## Usage
+定义一个 User model，继承 BaseModel，对年龄校验
+```
+from pydantic import (
+    UUID4,
+    BaseModel,
+    ConfigDict,
+    Field,
+    InstanceOf,
+    Json,
+    field_validator,
+    model_validator,
+    EmailStr, 
+    validator
+)
+class User(BaseModel):
+    name: str
+    age: int
+    email: EmailStr
+    phone: Optional[str] = None
+
+    @validator("age")
+    def check_age(cls, age):
+        if age < 18:
+            raise ValueError("用户年龄必须大于18岁")
+        return age
+
+```
+