Python Type Hints 從入門(mén)到實(shí)踐

name = "world"
def greeting(name):    return "Hello " + name
greeting(name)

name: str = "world"
def greeting(name: str) -> str:    return "Hello " + name
greeting(name)

def greeting(name: str = "world") -> str:    return "Hello " + name
greeting()

class Student(object):    def __init__(self, name, age):        self.name = name        self.age = age

def student_to_string(s: Student) -> str:    return f"student name: {s.name}, age: {s.age}."
student_to_string(Student("Tim", 18))

from typing import List, Tuple, Dict
l: List[int] = [1, 2, 3]
t: Tuple[str, ...] = ("a", "b")
d: Dict[str, int] = {    "a": 1,    "b": 2,}

l: list[int] = [1, 2, 3]
t: tuple[str, ...] = ("a", "b")
d: dict[str, int] = {    "a": 1,    "b": 2,}

config: list[tuple[str, int], dict[str, str]] = [    ("127.0.0.1", 8080),    {        "MYSQL_DB": "db",        "MYSQL_USER": "user",        "MYSQL_PASS": "pass",        "MYSQL_HOST": "127.0.0.1",        "MYSQL_PORT": "3306",    },]
def start_server(config: list[tuple[str, int], dict[str, str]]) -> None:    ...
start_server(config)

Config = list[tuple[str, int], dict[str, str]]

config: Config = [    ("127.0.0.1", 8080),    {        "MYSQL_DB": "db",        "MYSQL_USER": "user",        "MYSQL_PASS": "pass",        "MYSQL_HOST": "127.0.0.1",        "MYSQL_PORT": "3306",    },]
def start_server(config: Config) -> None:    ...
start_server(config)

def foo(*args: str, **kwargs: int) -> None:    ...
foo("a", "b", 1, x=2, y="c")

from typing import TypeVar
T = TypeVar("T")
def foo(*args: T, **kwargs: T) -> None:    ...
foo("a", "b", 1, x=2, y="c")

from typing import Union
T = Union[str, bytes]
def concat(s1: T, s2: T) -> T:    return s1 + s2
concat("hello", "world")concat(b"hello", b"world")concat("hello", b"world")concat(b"hello", "world")

from typing import TypeVar
T = TypeVar("T", str, bytes)
def concat(s1: T, s2: T) -> T:    return s1 + s2
concat("hello", "world")concat(b"hello", b"world")concat("hello", b"world")

from typing import Optional, Union
# None => type(None)def foo(arg: Union[int, None] = None) -> None:    ...

def foo(arg: Optional[int] = None) -> None:    ...

from typing import Any
def greeting(name):    return "Hello " + name

def greeting(name: Any) -> Any:    return "Hello " + name

from typing import Any
a: Any = Nonea = []  # 動(dòng)態(tài)語(yǔ)言特性a = 2
s: str = ''s = a  # Any 類型值賦給更精確的類型

from typing import Callable
def int_to_str(i: int) -> str:    return str(i)
def f(fn: Callable[[int], str], i: int) -> str:    return fn(i)
f(int_to_str, 2)

class Tree(object):    def __init__(self, left: "Tree" = None, right: "Tree" = None):        self.left = left        self.right = right
tree1 = Tree(Tree(), Tree())

from typing import Protocol
class Interface(Protocol):    def close(self) -> None:        ...
# class Stream(Interface):class Stream:    def close(self) -> None:        ...
def close_resource(r: Interface) -> None:    r.close()
f = open("a.txt")close_resource(f)
s: Stream = Stream()close_resource(s)

from dataclasses import dataclass, field

@dataclassclass User(object):    id: int    name: str    friends: list[int] = field(default_factory=list)

data = {    "id": 123,    "name": "Tim",}
user = User(**data)print(user.id, user.name, user.friends)# > 123 Tim []

class User(object):    def __init__(self, id: int, name: str, friends=None):        self.id = id        self.name = name        self.friends = friends or []

data = {    "id": 123,    "name": "Tim",}
user = User(**data)print(user.id, user.name, user.friends)# > 123 Tim []

from datetime import datetimefrom typing import Optional
from pydantic import BaseModel

class User(BaseModel):    id: int    name = 'John Doe'    signup_ts: Optional[datetime] = None    friends: list[int] = []

external_data = {    'id': '123',    'signup_ts': '2021-09-02 17:00',    'friends': [1, 2, '3'],}user = User(**external_data)
print(user.id)# > 123print(repr(user.signup_ts))# > datetime.datetime(2021, 9, 2, 17, 0)print(user.friends)# > [1, 2, 3]print(user.dict())"""{    'id': 123,    'signup_ts': datetime.datetime(2021, 9, 2, 17, 0),    'friends': [1, 2, 3],    'name': 'John Doe',}"""

from pydantic import ValidationError
try:    User(signup_ts='broken', friends=[1, 2, 'not number'])except ValidationError as e:    print(e.json())"""[  {    "loc": [      "id"    ],    "msg": "field required",    "type": "value_error.missing"  },  {    "loc": [      "signup_ts"    ],    "msg": "invalid datetime format",    "type": "value_error.datetime"  },  {    "loc": [      "friends",      2    ],    "msg": "value is not a valid integer",    "type": "type_error.integer"  }]"""

class MySQLHandler(object):    """MySQL handler"""
    def __init__(self):        self.conn = pymysql.connect(            host=DB_HOST,            port=DB_PORT,            user=DB_USER,            password=DB_PASS,            database=DB_NAME,            charset=DB_CHARSET,            client_flag=CLIENT.MULTI_STATEMENTS,  # execute multi sql statements        )        self.cursor = self.conn.cursor()
    def __del__(self):        self.cursor.close()        self.conn.close()
    @contextmanager    def execute(self):        try:            yield self.cursor.execute            self.conn.commit()        except Exception as e:            self.conn.rollback()            logging.exception(e)
    @contextmanager    def executemany(self):        try:            yield self.cursor.executemany            self.conn.commit()        except Exception as e:            self.conn.rollback()            logging.exception(e)
    def _tuple_to_object(self, data: List[tuple]) -> List[FetchObject]:        obj_list = []        attrs = [desc[0] for desc in self.cursor.description]        for i in data:            obj = FetchObject()            for attr, value in zip(attrs, i):                setattr(obj, attr, value)            obj_list.append(obj)        return obj_list
    def fetchone(self) -> Optional[FetchObject]:        result = self.cursor.fetchone()        return self._tuple_to_object([result])[0] if result else None
    def fetchmany(self, size: Optional[int] = None) -> Optional[List[FetchObject]]:        result = self.cursor.fetchmany(size)        return self._tuple_to_object(result) if result else None
    def fetchall(self) -> Optional[List[FetchObject]]:        result = self.cursor.fetchall()        return self._tuple_to_object(result) if result else None

from inspect import getfullargspecfrom functools import wrapsfrom typing import get_type_hints

def type_check(fn):    @wraps(fn)    def wrapper(*args, **kwargs):        fn_args = getfullargspec(fn)[0]        kwargs.update(dict(zip(fn_args, args)))        hints = get_type_hints(fn)        hints.pop("return", None)        for name, type_ in hints.items():            if not isinstance(kwargs[name], type_):                raise TypeError(f"expected {type_.__name__}, got {type(kwargs[name]).__name__} instead")        return fn(**kwargs)
    return wrapper

# name: str = "world"name: int = 2
@type_checkdef greeting(name: str) -> str:    return str(name)
print(greeting(name))# > TypeError: expected str, got int instead