mypythontools.property package

Module contains MyProperty class that is alternative to normal python property. It’s implemented via descriptor and edited __get__ and __set__ magic methods.

There is default setter, it’s possible to auto init values on class init and values in setter are validated on python 3.9 and newer. This result in much less code written when using a lot of similar properties.

First call is lazy evaluated during first call.

Example of how can it be used is in module config.

Examples:

>>> from typing_extensions import Literal
...
>>> class Example:
...     def __init__(self) -> None:
...         init_my_properties(self)
...
...     @MyProperty
...     def var(self) -> int:  # Type hints are validated.
...         '''
...         Type:
...             int
...
...         Default:
...             123
...
...         This is docstrings (also visible in IDE, because not defined dynamically).
...         Also visible in Sphinx documentation.'''
...
...         return 123  # This is initial value that can be edited.
...
...     @MyProperty
...     def var_literal(self) -> Literal[1, 2, 3]:  # Literal options are also validated
...         return 2
...
...     @MyProperty
...     def evaluated(self) -> int:  # If other defined value is change, computed property is also updated
...         return self.var + 1
...
>>> config = Example()
>>> config.var
123
>>> config.var = 665
>>> config.var
665
>>> config.var = "String is problem"  
Traceback (most recent call last):
TypeError: ...
...
>>> config.var_literal = 4  
Traceback (most recent call last):
TypeError: ...
...
>>> config.var = 665  # Restoring value as on 3.9 it's no validated, so test would fails
>>> config.evaluated
666

You can still setup a function (or lambda expression) as a new value and returned value still will be validated

>>> config.var = lambda self: self.var_literal + 1

mypythontools.property.MyProperty(f: Callable[[...], T]) → MyPropertyClass[T]

Wrap MyProperty to work as expected.

If not using this workaround, but use class decorator, IDE complains that property has no defined setter.

Parameters

f (Callable[..., T]) – Usually it’s decorated method from class. It can be static as well.

class mypythontools.property.MyPropertyClass(fget: Callable[[...], T], doc=None)

Bases: property, Generic[T]

Python property on steroids. Check module docstrings for more info.

default_fset(used_object, content) → None

Define how new values will be stored.

mypythontools.property.init_my_properties(self)

Init private values of properties.

Property usually get value of some private variable. This leads to many unnecessary code sometimes.