A simple package that allows having class-level properties and validator for typical configuration classes.
Project description
Class utilities
Author: David Salac https://github.com/david-salac
Simple package with helpful utilities for classes. That includes class level properties and filters for configuration classes.
Note: this package does not require any external dependencies.
How to install package
Use PIP command:
pip install classutilities
How to use class level properties
Class level properties are properties defined on class level. They behave exactly the same as normal properties (but allow being called on class level and not only on instance level).
Consider the following example (defining class level properties):
import classutilities
class SomeClass(classutilities.ClassPropertiesMixin):
_some_variable = 8 # Some class variable
@classutilities.classproperty
def some_variable(cls): # Example of getter
return cls._some_variable
@some_variable.setter
def some_variable(cls, value): # Example of setter
cls._some_variable = value
ClassPropertiesMixin
allows you to use a setter for
properties. However, if you only need a getter, it will
work even without this mixin.
Usage of class-level properties:
# Getter:
value = SomeClass.some_variable
print(value) # >>> 8
# Setter:
new_value = 9
SomeClass.some_variable = new_value
print(SomeClass.some_variable) # >>> 9
print(SomeClass._some_variable) # >>> 9
As you can see, class-level properties behave very naturally.
Configuration classes
Configuration classes usually follow standard patterns, mainly:
- All members have to be upper case (if they do not start with an underscore).
- There is no constructor in the class.
- There is no standard (instance) method in the class. Only class methods and static methods are allowed.
It is beneficial to have some validator for a configuration class that checks if all these conditions are followed. This is precisely what ConfigClassMixin does. Consider the following use-case:
import classutilities
class SomeConfigClass(classutilities.ConfigClassMixin):
# This is OK:
DATABASE_HOST = "localhost" # OK: variable name in uppercase
DATABASE_NAME = "testing" # OK: variable name in uppercase
# ...
# This is NOT OK (class variables must be uppercase):
database_password = "pass" # NO: must not be lowercase
# This is OK (underscore on the beginning):
_api_version = "1.0.0" # OK: starts with an underscore
# This is OK:
@classmethod
def connect_to_database(cls): # Class methods are acceptable
return ...
# This is OK:
@staticmethod
def check_status(): # Static methods are acceptable
return ...
# This is NOT OK:
def check_parameters(self): # No instance-level methods
return ...
Mixin ConfigClassMixin
can be used together with
mixin for class-level properties. Class level properties
are also acceptable (this filter allows them).
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