python-access-modifiers 1.3.1

Python decorators to specify accessible scopes and enhance access control of methods.

Installation

Built and tested on Python 3.12.
No requirements other than the module itself.

pip install python-access-modifiers

Introduction

python-access-modifiers is a lightweight Python package designed to enhance access control of methods within classes and modules.

Decorators

@private - Defines a method as private, controlling the accessibility of the method based on the calling context. Private methods can only be invoked from inside of the same scope as the defining method.
@protected - Defines a method as protected, allowing the method to be invoked from the defining class and any classes that inherit from it.
@constant - Defines a method as constant, removing the ability for the method to be overriden. Note that this decorator can only be used within a class.
@field_access_modifiers - Allows a class to modify the accessibility of fields, defining them as public or protected.

Example Usage

Creating a private method inside of a class

from python_access_modifiers import private

class MyClass():
    @private
    def my_private_method(self) -> None:
        print("This is a private method")

    def my_public_method(self) -> None:
        print("This is a public method")
        self.my_private_method()

my_class = MyClass()
my_class.my_public_method()

Output

No exception is raised because my_private_method is called from within MyClass, not from outside of the accessible scope.

This is a public method
This is a private method

Calling a private method outside of the accessible scope

from python_access_modifiers import private

class MyClass():
    @private
    def my_private_method(self) -> None:
        print("This is a private method")

    def my_public_method(self) -> None:
        print("This is a public method")
        self.my_private_method()

my_class = MyClass()
my_class.my_private_method()

Output

RuntimeError: Cannot invoke private method "MyClass.my_private_method" from within the scope of "__main__"

Creating classes that inherit private methods

from python_access_modifiers import private

class Base():
    @private
    def my_private_method(self) -> None:
        print("This is a private method")

    def my_public_method(self) -> None:
        print("This is a public method")
        self.my_private_method()

class Child(Base):
    ...

child = Child()
child.my_public_method()

Output

my_private_method is called from within the Base class, therefore no exception is raised.

This is a public method
This is a private method

However, if my_private_method was called directly from outside of the accessible scope of the Base class, a RuntimeError would be raised.

child = Child()
child.my_private_method()

Output

RuntimeError: Cannot invoke private method "Base.my_private_method" from within the scope of "__main__"

Creating a private method from inside of a module

my_module.py

from python_access_modifiers import private

@private
def my_private_method() -> None:
    print("This method is private to my_module")

main.py

from my_module import my_private_method

my_private_method()

Output

RuntimeError: Cannot invoke private method "my_module.my_private_method" from module "__main__"

Creating a protected method

from python_access_modifiers import protected

class MyBaseClass():
    @protected
    def my_protected_method(self) -> None:
        print("This method is protected inside of MyBaseClass")

    def call_protected_method(self) -> None:
        self.my_protected_method()

class MySubClass(MyBaseClass):
    def call_protected_method_from_subclass(self) -> None:
        self.my_protected_method()
        
subclass = MySubClass()

subclass.call_protected_method()
subclass.call_protected_method_from_subclass()

Output

If my_protected_method is called from within MyBaseClass or from within one of it's subclasses (i.e: MySubClass), the method gets called normally.

This method is protected inside of MyBaseClass
This method is protected inside of MyBaseClass

However, if my_protected_method is called from outside of the accessible scope of the base class and it's subclasses, an exception will be raised.

subclass.my_protected_method()

Output

RuntimeError: Cannot invoke protected method "MyBaseClass.my_protected_method" from within the scope of "__main__"

Creating a constant method

Constant methods can only be created from inside of a class

from python_access_modifiers import constant

class MyClass():
    @constant
    def my_constant_method(self) -> None:
        print("This method is constant")

my_class = MyClass()
my_class.my_constant_method()

Output

This method is constant

Attempting to modify a constant method

def modified_method(self) -> None:
    print("This method has been modified")

my_class.my_constant_method = modified_method

Output

RuntimeError: "my_constant_method" is constant and cannot be overriden

Modifying the accessibility of fields

The accessibility of fields can only be modified from within classes. Currently, you can only create Protected fields. Fields are public by default.

Creating a protected field

from python_access_modifiers import field_access_modifiers, Protected

@field_access_modifiers
class MyClass():
    protected_field: Protected[int]
    
    def __init__(self, value: int) -> None:
        self.protected_field: int = value

    def show_protected_value(self) -> None:
        print(self.protected_field)

my_class = MyClass(7)
my_class.show_protected_value()

Output

7

Field access modifiers can be used with or without a type generic.

>>> field: Protected
>>> bool_field: Protected[bool]
>>> int_or_float_field: Protected[int | float]

Attempting to access a protected field

print(my_class.protected_field)

Output

RuntimeError: Cannot access protected field "MyClass.protected_field" from within "<module>"