Implementing Type Checking in Decorators
To effectively handle type errors in decorator functions, you can implement type checking within the decorator itself. This ensures that the decorated function receives the correct arguments and returns the expected data type.
Using Type Annotations
One way to implement type checking in decorators is by leveraging Python's type annotation feature. Type annotations allow you to specify the expected data types of function parameters and return values.
from typing import Callable, Any
def my_decorator(func: Callable[[int, int], int]) -> Callable[[int, int], int]:
def wrapper(x: int, y: int) -> int:
return func(x, y)
return wrapper
@my_decorator
def add(a: int, b: int) -> int:
return a + b
result = add(5, 10) ## Works as expected
result = add(5, "10") ## TypeError: add() argument 2 must be int, not str
In this example, the my_decorator()
function uses type annotations to specify that the decorated function must take two integer arguments and return an integer. This ensures that any function decorated with my_decorator()
will be checked for the correct input and output types.
Using Type Checking Libraries
Another approach is to use type checking libraries, such as mypy
or pydantic
, to enforce type constraints within your decorator functions.
from pydantic import BaseModel, validator
from typing import Callable, Any
class AddInput(BaseModel):
a: int
b: int
def my_decorator(func: Callable[[AddInput], int]) -> Callable[[AddInput], int]:
def wrapper(input_data: AddInput) -> int:
return func(input_data)
return wrapper
@my_decorator
def add(input_data: AddInput) -> int:
return input_data.a + input_data.b
result = add(AddInput(a=5, b=10)) ## Works as expected
result = add(AddInput(a=5, b="10")) ## ValidationError: 1 validation error for AddInput
## b
## value is not a valid integer (type=type_error.integer)
In this example, the pydantic
library is used to define a BaseModel
class (AddInput
) that specifies the expected types for the a
and b
attributes. The my_decorator()
function then ensures that the decorated function receives an AddInput
instance, and any type violations will result in a ValidationError
.
By implementing type checking within your decorator functions, you can catch type-related errors early in the development process and ensure that your decorated functions are used correctly.