Type hints & mypy

hint.py - chạy y hệt bản không hint

def cong(a: int, b: int) -> int:   # a, b la int; tra ve int
    return a + b

ten: str = "An"
diem: list[int] = [8, 9, 10]
print(cong(2, 3))

5

chạy mypy + soi kiểu bằng reveal_type

# app.py
def cong(a: int, b: int) -> int:
    return a + b

reveal_type(cong(2, 3))     # cong cu phap cua mypy de SOI kieu

# Chay:
#   uv run --with mypy mypy app.py
# mypy in:
#   app.py: note: Revealed type is "builtins.int"

modern.py

def tong(ds: list[int]) -> int:
    return sum(ds)

def diem(d: dict[str, int], ten: str) -> int | None:
    return d.get(ten)                 # int neu co, None neu khong

def dau_tien[T](ds: list[T]) -> T:    # generic PEP 695 (3.12+)
    return ds[0]

type Vector = list[float]             # bi danh kieu

print(tong([1, 2, 3]), diem({"An": 9}, "Binh"), dau_tien(["x", "y"]))

6 None x

protocol.py

from typing import Protocol, runtime_checkable

@runtime_checkable
class Keu(Protocol):
    def keu(self) -> str: ...        # ai co .keu() deu "la Keu"

class Cho:
    def keu(self): return "Gau"
class Xe:
    def chay(self): return "vroom"

def cho_keu(x: Keu) -> str:          # nhan BAT KY thu gi co .keu()
    return x.keu()

print(cho_keu(Cho()))                # OK
print(isinstance(Cho(), Keu), isinstance(Xe(), Keu))   # runtime_checkable
# cho_keu(Xe())  -> mypy: incompatible type "Xe"; expected "Keu"

Gau
True False

typeddict_literal.py

from typing import TypedDict, Literal

class NguoiDung(TypedDict):           # dict CO kieu cho tung khoa
    ten: str
    tuoi: int

u: NguoiDung = {"ten": "An", "tuoi": 20}   # thieu khoa / sai kieu -> mypy bao

def set_che_do(m: Literal["doc", "ghi"]) -> None:   # chi nhan 2 gia tri
    ...

set_che_do("doc")                     # OK
# set_che_do("xoa")  -> mypy: incompatible type Literal['xoa']; expected Literal['doc','ghi']

runtime_hints.py

from typing import get_type_hints

def cong(a: int, b: int) -> int:
    return a + b

print(cong.__annotations__)          # {'a': int, 'b': int, 'return': int}
print(get_type_hints(cong))          # tuong tu, da giai ten kieu chuan hon

{'a': <class 'int'>, 'b': <class 'int'>, 'return': <class 'int'>}
{'a': <class 'int'>, 'b': <class 'int'>, 'return': <class 'int'>}