# exdec
[](https://pypi.org/project/exdec) [](https://github.com/EvgeniyBurdin/exdec/actions/workflows/python-app.yml) [](https://codecov.io/gh/EvgeniyBurdin/exdec) [](https://lgtm.com/projects/g/EvgeniyBurdin/exdec/alerts/) [](https://lgtm.com/projects/g/EvgeniyBurdin/exdec/context:python)
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:
```python
# 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
```bash
pip install exdec
```
## Quick start
More examples in the [examples folder](https://github.com/EvgeniyBurdin/exdec/tree/main/examples).
```python
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
```