advanced-descriptors 4.0.4

Advanced descriptors for special cases.

Advanced descriptors

This package includes helpers for special cases:

• SeparateClassMethod - allow to have classmethod and normal method both with the same name.

• AdvancedProperty - property with possibility to set class wide getter.

• LogOnAccess - property with logging on successful get/set/delete or failure.

SeparateClassMethod

This descriptor can be set using standard decorator syntax. Create instance with arguments:

def imeth(instance):
    return instance.value

def cmeth(owner):
    return owner.value

class Target(object):
    value = 1

    def __init__(self):
        self.value = 2
    getval = advanced_descriptors.SeparateClassMethod(
        imeth, cmeth
    )

Create instance wrapping as decorator:

class Target(object):
    value = 1

    def __init__(self):
        self.value = 2

    @advanced_descriptors.SeparateClassMethod
    def getval(self):
        return self.value

    @getval.class_method
    def getval(cls):
        return cls.value

Cases with method only and classmethod only is useless: method as-is and @classmethod should be used in corresponding cases.

Note

classmethod receives class as argument. IDE’s don’t know about custom descriptors and substitutes self by default.

AdvancedProperty

This descriptor should be used in cases, when in addition to normal property API, class getter is required. If class-wide setter and deleter also required - you should use standard propery in metaclass.

Usage examples:

1. In addition to normal property API:

class Target(object):
    _value = 777

    def __init__(self):
        self._value = 42

    @advanced_descriptors.AdvancedProperty
    def val(self):
        return self._value

    @val.setter
    def val(self, value):
        self._value = value

    @val.deleter
    def val(self):
        self._value = 0

    @val.cgetter
    def val(cls):
        return cls._value

2. Use class-wide getter for instance too:

class Target(object):
    _value = 1

    val = advanced_descriptors.AdvancedProperty()

    @val.cgetter
        def val(cls):
            return cls._value

Note

class-wide getter receives class as argument. IDE’s don’t know about custom descriptors and substitutes self by default.

LogOnAccess

This special case of property is useful in cases, where a lot of properties should be logged by similar way without writing a lot of code.

Basic API is conform with property, but in addition it is possible to customize logger, log levels and log conditions.

Usage examples:

1. Simple usage. All by default. logger is re-used from instance if available with names logger or log else used internal advanced_descriptors.log_on_access logger:

import logging

class Target(object):

    def init(self, val='ok')
        self.val = val
        self.logger = logging.get_logger(self.__class__.__name__)  # Single for class, follow subclassing

    def __repr__(self):
        return "{cls}(val={self.val})".format(cls=self.__class__.__name__, self=self)

    @advanced_descriptors.LogOnAccess
    def ok(self):
        return self.val

    @ok.setter
    def ok(self, val):
        self.val = val

    @ok.deleter
    def ok(self):
        self.val = ""

2. Use with global logger for class:

class Target(object):

  def init(self, val='ok')
      self.val = val

  def __repr__(self):
      return "{cls}(val={self.val})".format(cls=self.__class__.__name__, self=self)

  @advanced_descriptors.LogOnAccess
  def ok(self):
      return self.val

  @ok.setter
  def ok(self, val):
      self.val = val

  @ok.deleter
  def ok(self):
      self.val = ""

  ok.logger = 'test_logger'
  ok.log_level = logging.INFO
  ok.exc_level = logging.ERROR
  ok.log_object_repr = True  # As by default
  ok.log_success = True  # As by default
  ok.log_failure = True  # As by default
  ok.log_traceback = True  # As by default
  ok.override_name = None  # As by default: use original name

Testing

The main test mechanism for the package advanced-descriptors is using tox. Available environments can be collected via tox -l

CI systems

For CI/CD GitHub actions is used:

GitHub actions: is used for checking: PEP8, pylint, bandit, installation possibility and unit tests.