Easily debug and trace attribute changes in your Python classes
pip install attr-tracers
To use this module, simply import trace
from it, and decorate your chosen class:
from tracers import trace
@trace("test")
class MyClass:
def __init__(self) -> None:
self.test = 0
...
You can set custom setter and getter methods for your trace, practically allowing you to subcribe to read/write events of an attribute.
from typing import Any
from tracers import trace
def handle_get(obj: object) -> Any:
"""Get variable"""
# Note the namespace-based reference to `attr`
print(f"Trying to get {attr} from {obj}")
return getattr(obj, "_" + attr)
def handle_set(obj: object, new: Any) -> None:
"""Set variable"""
print(f"Setting {attr} for {obj} from {getattr(obj, attr)} -> {new}")
setattr(obj, "_" + attr, new)
attr = "test"
@trace(attr, getter=handle_get, setter=handle_set)
class MyClass:
def __init__(self) -> None:
self.test = 0
You can also optionally output traces into a file non-interactively using the output
argument.
Please note that these methods do NOT get a reference to attr
. This is a quirk of properties, but you can work around it using namespace-based referencing, like above.
This module under the hood is just an easy way to assign properties to a class.
When decorated with trace("attr")
, a class has its attribute attr
replaced with a property. The default setter and getter of this property access the "_attr" attribute, as the property takes up "attr".
Essentially, what it becomes is this:
class MyClass:
@property
def attr(self) -> Any:
return self._attr
@attr.setter
def attr(self, new: str) -> None:
# Display current trace
# Take input, quit or dismiss if chosen
self._attr = new
While defining the properties manually is doable, this module comes in really handy for debugging.
Imagine having a pretty complex hierarchy of class-inheritance and objects all relating to eachother (like it happens in pytermgui).
It often happens that there is a certain attribute that isn't quite behaving how it is supposed to. While you could define these properties yourself, being able to import trace
and plop it on top of a class is really efficient for debugging.
It also looks much nicer!