exdec

Decorator for catching exceptions in functions and methods. And also with the possibility of preliminary processing of incoming data, and post-processing of the function result.

• Works with both synchronous and asynchronous functions and methods;
• Catches exceptions of the required types;
• Three types of handlers are available: before the start of the function, after its end, and the exception handler;
• Handlers can be both synchronous and asynchronous;
• All current information about the function is available in any handler;
• Ability to change the incoming data and the result of the function in the handlers;
• Several ways to fine-tune and pre-configure the decorator;

Decorator arguments

name	annotation	default
All positional arguments (i.e. *args)	Type[Exception]	Exception
exclude	bool	False
before_handler	Optional[Callable[[FuncInfo],None]]	None
after_handler	Optional[Callable[[FuncInfo],None]]	None
exc_handler	Callable[[FuncInfo],Any]	exdec.utils.default_exc_handler
extra	Any	None
manager	exdec.manager.Manager	Manager()

If exclude set to False, then exc_handler will handle exceptions from *args. If set to True, then exc_handler will handle all exceptions except those specified in *args.

In the extra argument you can specify arbitrary data to be passed to the handlers.

All handlers have an FuncInfo argument:

# exdec/data_classes.py

@dataclass
class FuncInfo:
    """ Decorated function information.

    `result` will be available in the handler after calling the function if
    no exception occurs.

    If an exception occurs during the execution of the function, it will be
    stored in `exception`. This information will be available in the exception
    handler.
    """
    func: Callable
    args: Tuple[Any, ...]
    kwargs: Dict[str, Any]
    result: Any = None
    exception: Optional[Exception] = None
    extra: Any = None
    
...

Installation

pip install exdec

Quick start

More examples in the examples folder.

from typing import Optional

from exdec.data_classes import FuncInfo
from exdec.decorator import catch


# 1 --------------------------------------------------------------------------

# Catching all exceptions
@catch
def safe_div_1(x: int, y: int) -> Optional[float]:
    return x / y


assert safe_div_1(3, 3) == 1.0
assert safe_div_1(3, 0) is None


# 2 --------------------------------------------------------------------------

# Catching only ZeroDivisionError
@catch(ZeroDivisionError)
def safe_div_2(x: int, y: int) -> Optional[float]:
    return x / y


assert safe_div_2(3, 0) is None


# 3 --------------------------------------------------------------------------

HANDLER_RESULT = 0.0


def exc_handler(func_info: FuncInfo) -> float:
    msg = f"Caught an exception! func_info={func_info}."
    print(f"{msg} Result changed to {HANDLER_RESULT}")
    return HANDLER_RESULT


# Catching only ZeroDivisionError
@catch(ZeroDivisionError, exc_handler=exc_handler)
def safe_div_3(x: int, y: int) -> float:
    return x / y


assert safe_div_3(3, 0) == HANDLER_RESULT


# 4 --------------------------------------------------------------------------

class MyException_1(Exception):
    pass


class MyException_2(Exception):
    pass


# Catching all exceptions, except for (MyException_1, MyException_2)
@catch(MyException_1, MyException_2, exclude=True, exc_handler=exc_handler)
def safe_div_4(x: int, y: int) -> float:
    return x / y


assert safe_div_4(3, 0) == HANDLER_RESULT


# 5 --------------------------------------------------------------------------

# For methods everything works the same
class MathFunctions:

    # Catching only ZeroDivisionError
    @catch(ZeroDivisionError)
    def safe_div_5(self, x: int, y: int) -> Optional[float]:
        return x / y


math_functions = MathFunctions()
assert math_functions.safe_div_5(3, 0) is None


# 6 --------------------------------------------------------------------------

def exc_handler_reraise(func_info: FuncInfo) -> float:
    print(f"Caught an exception! func_info={func_info}. \n RERAISE!")
    raise func_info.exception


# Catching only (MyException_1, ZeroDivisionError) and reraise
@catch(MyException_1, ZeroDivisionError, exc_handler=exc_handler_reraise)
def div_6(x: int, y: int) -> float:
    return x / y


div_6(3, 0)  # ZeroDivisionError