众所周知，一个强的类型系统对代码的可读性，可维护性，减少bug数都至关重要，当python开始支持type hints时我就一直想着在新的项目中将这个特性落地（备注：python的类型系统目前只是语法糖，不是解释器层面的，但是其价值语法糖层面的价值依然值得大家去尝试），以下是我之前整理的一些关于typed python的笔记，分享给大家。

基本数据类型使用例子

• int
• float
• bool
• bytes
• str

def get_items(item_a: str, item_b: int, item_c: float, item_d: bool, item_e: bytes):
    return item_a, item_b, item_c, item_d, item_d, item_e

复合类型

• 列表类型

from typing import List


def process_items(items: List[str]):
    for item in items:
        print(item)

• 元组和集合类型

from typing import Set, Tuple


def process_items(items_t: Tuple[int], items_s: Set[bytes]):
    return items_t, items_s

• 字典类型

from typing import Dict


def process_items(prices: Dict[str, float]):
    for item_name, item_price in prices.items():
        print(item_name)
        print(item_price)

• Class类型

class Person:
    def __init__(self, name: str):
        self.name = name


def get_person_name(one_person: Person):
    return one_person.name

• 函数类型

from typing import Callable

def on_event(self, event_type: str) -> Callable:
    def f():
        return "this is callable"
    return f

不确定类型和多个可能类型

• 不确定类型

from typing import Any

def test(a: Any) -> Any:
    return a

• 返回多个类型可能的类型

from typing import Union

def test_union(a: Union(int, None)) -> Union(int, None):
    return a

基于typed python的schema库

• pydantic是基于typing python的schema库

from datetime import datetime
from typing import List
from pydantic import BaseModel


class User(BaseModel):
    """
    在pydantic中有默认值的为非必传参数，没有默认值的为必传参数
    显示类型表示只接受该类型入参，会自动进行检查校验
    """
    id: int
    name = 'John Doe'
    signup_ts: datetime = None
    friends: List[int] = []

external_data = {
    'id': '123',
    'signup_ts': '2019-06-01 12:22',
    'friends': [1, 2, '3']
}
user = User(**external_data)
print(user.id)
print(repr(user.signup_ts))
print(user.friends)
print(user.dict())

pydantic支持常见的参数验证和扩展验证模式

from pydantic import BaseModel, ValidationError, validator

class UserModel(BaseModel):
    name: str
    username: str
    password1: str
    password2: str

    @validator('name')
    def name_must_contain_space(cls, v):
        if ' ' not in v:
            raise ValueError('must contain a space')
        return v.title()

    @validator('password2')
    def passwords_match(cls, v, values, **kwargs):
        if 'password1' in values and v != values['password1']:
            raise ValueError('passwords do not match')
        return v

    @validator('username')
    def username_alphanumeric(cls, v):
        assert v.isalpha(), 'must be alphanumeric'
        return v

print(UserModel(name='samuel colvin', username='scolvin', password1='zxcvbn',
                password2='zxcvbn'))
#> name='Samuel Colvin' username='scolvin' password1='zxcvbn' password2='zxcvbn'

try:
    UserModel(name='samuel', username='scolvin', password1='zxcvbn',
              password2='zxcvbn2')
except ValidationError as e:
    print(e)
"""
2 validation errors for UserModel
name
  must contain a space (type=value_error)
password2
  passwords do not match (type=value_error)
"""

命令行解析工具click集成type hint特性

typer可以把click和typing hint特性整合的工具库

• typer

import typer

app = typer.Typer()


@app.command()
def hello(name: str):
    typer.echo(f"Hello {name}")


@app.command()
def goodbye(name: str, formal: bool = False):
    if formal:
        typer.echo(f"Goodbye Ms. {name}. Have a good day.")
    else:
        typer.echo(f"Bye {name}!")


if __name__ == "__main__":
    app()