Proper access modifiers for Python classes.
Project description
pyattr
While Python does have name mangling, it is not nearly as powerful as access modifiers found in languages such as C++. pyattr provides an easy-to-use API for access modifiers in Python.
Installation
Installation via pip:
pip install pyattr
Usage
All you have to do is make your class inherit from the pyattr.Pyattr
class, and add super().__init__()
as the first line in the __init__
function of your class. And that's it! pyattr will handle the magic to make sure variables cannot be accessed / set where the shouldn't be. It also provides useful error messages to users.
Example
Here is a simple example involving a private variable.
from pyattr import Pyattr
class Example(Pyattr):
def __init__(self) -> None:
super().__init__()
self.__name = "pyattr"
example = Example()
print(example.__name) # Error - '__name' is a private attribute of 'Example'.
As well as variables, pyattr also supports access control of functions!
from pyattr import Pyattr
class Example(Pyattr):
def __init__(self) -> None:
super().__init__()
def __example(self) -> None:
pass
example = Example()
print(example.__example()) # Error - '__example' is a private attribute of 'Example'.
How it works
Note For a more in-depth explanation on how pyattr works, see my blog post.
pyattr overrides the default set and get functions of your class. The overridden functions defined by pyattr are merged into your class when you inherit from the pyattr.Pyattr
class. As well as this, the pyattr.Pyattr
class inherits from the pyattr._PyattrDict
class, which provides a custom dictionary implementation. This is because you can change the variables in a class using class.__dict__["var"] = "val"
, meaning a custom dictionary would be the best way to prevent the access system being circumvented.
The overriden set and get functions of your class call the respective set and get functions of the custom dictionary. This dictionary, using sys._getframe()
, works out the caller's function, and the caller's class (if any). It uses this data to work out if the caller should be allowed to access the specified variables. If it shouldn't, an AttributeError
is raised, with an error message explaining the cause.
Benchmarks
The code for the benchmarks can be found in the benchmark folder.
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