Python type hints và Pydantic v2

from typing import NotRequired, Protocol, TypedDict, runtime_checkable
 
class Iface(TypedDict):          # dict có key cố định, ví dụ JSON từ API
    name: str
    mtu: int
    descr: NotRequired[str]      # key có thể vắng
 
@runtime_checkable
class Driver(Protocol):          # "duck typing" có kiểm tra: class nào có get_facts() là hợp lệ
    def get_facts(self) -> dict[str, str]: ...
 
def collect(drv: Driver) -> dict[str, str]:
    return drv.get_facts()

from enum import StrEnum
from ipaddress import IPv4Address, IPv4Interface
from typing import Annotated, Literal, Self
 
from pydantic import (AfterValidator, AliasChoices, BaseModel, ConfigDict, Field,
                      SecretStr, computed_field, field_validator, model_validator)
 
class Status(StrEnum):
    UP = "up"
    DOWN = "down"
 
def check_port(v: int) -> int:
    if not 1 <= v <= 65535:
        raise ValueError("port out of range")
    return v
 
Port = Annotated[int, AfterValidator(check_port)]   # kiểu tái sử dụng được
 
class Interface(BaseModel):
    model_config = ConfigDict(extra="forbid", str_strip_whitespace=True)
    name: str = Field(min_length=1)
    ip: IPv4Interface | None = None                  # "192.0.2.1/31"
    mtu: int = Field(default=1500, ge=576, le=9216)  # "9000" -> 9000 (lax mode)
    status: Status = Status.UP
    tags: list[str] = Field(default_factory=list)
 
    @field_validator("name")
    @classmethod
    def lower(cls, v: str) -> str:
        return v.lower()
 
class Device(BaseModel):
    hostname: str = Field(validation_alias=AliasChoices("hostname", "name"))
    platform: Literal["iosxr", "junos"]
    mgmt_ip: IPv4Address
    ssh_port: Port = 22
    password: SecretStr | None = None                # in ra thành '**********'
    interfaces: list[Interface] = []
 
    @model_validator(mode="after")
    def no_telnet(self) -> Self:                     # kiểm tra chéo nhiều field
        if self.ssh_port == 23:
            raise ValueError("telnet port not allowed")
        return self
 
    @computed_field  # type: ignore[prop-decorator]
    @property
    def fqdn(self) -> str:
        return f"{self.hostname}.example.net"

from pydantic import ValidationError
 
try:
    Device(hostname="x", platform="eos", mgmt_ip="1.2.3", ssh_port=0)
except ValidationError as e:
    for err in e.errors():                 # 3 lỗi được gom trong một lần
        print(err["loc"], err["type"], err["msg"])
# ('platform',) literal_error ...
# ('mgmt_ip',) ip_v4_address ...
# ('ssh_port',) value_error ...