5.3. The Supported Class Features

The package namedtuplex provides the abstract base class NamedTupleXABC of type NamedTupleXABCMeta for factories of named tuples with configurable inheritance features.

from __future__ import print_function

from namedtuplex.abc import NamedTupleXABC

class MyClass(NamedTupleXABC):
    _fields = ('name0', 'name1',)

x = MyClass(11, 22)

print(x.name0)
print(x[0])

print(x.name1)
print(x[1])

The parameters for the control of the derivation could be simply set by class member variables. The classes could serve as base classes and mixin-classes themself.

5.3.1. Abstract Inheritance

The class NamedTupleXABC could be used as a base class for abstract classes including the mixin of multiple derived abstract classes.

from __future__ import print_function

from namedtuplex.abc import NamedTupleXABC


class MyClassABC(NamedTupleXABC):
    myvar0 = 4711
    myvar1 = 815

    @property
    def myvalue(self):
        return self.myvar0 + self.myvar1


class MyClass(MyClassABC):
    _fields = ('name0', 'name1',)  # chnages now to a non-abstract class


x = MyClass(11, 22)

print(x.name0)
print(x[0])

print(x.name1)
print(x[1])

print(x.myvalue)

The presence of the member variable _fields determines hereby the transformation of an abstract class into a non-abstract class.

5.3.2. Non-Abstract Inheritance

The resulting non-abstract classes could serve as base classes again, including to be used as mixin-classes.

from __future__ import print_function

from namedtuplex.abc import ABC


class MyMixin(object):
    myvar = 4711


class MyClassABC(ABC):
    _fields = ('name2', 'name3',)  # chnages now to a non-abstract class


class MyClass(MyClassABC, MyMixin):
    _fields = ('name0', 'name1',)  # chnages now to a non-abstract class


x = MyClass(11, 22, 33, 44)

print(x)

The main difference of “transformed” non-abstract classes to the standard inheritance is here the optional control of the processing of the special class member variables for the configuration of the named tuple factory. The class member _merge controls, whether these will be superposed by derived classes, or merged into the corresponding class variables of the derived class.

from __future__ import print_function

from namedtuplex.abc import ABC


class MyMixin(ABC):
    _fields = ('name2', 'name3',)  # chnages now to a non-abstract class


class MyClassABC(object):
    myvar = 4711


class MyClass(MyClassABC, MyMixin,):
    _fields = ('name0', 'name1',)  # chnages now to a non-abstract class
    _merge = False


x = MyClass(11, 22,)

print(x)

This behaviour could be altered for each inheritance level separately.

5.3.3. Default Values

The metaclass NamedTupleXABCMeta uses a variable as the reference to the factory for the named tuple. The metaclass relies hereby for the feature of default values on the selected factory. The default factory is namedtupledefs.namedtuple [namedtupledefs], which is a patched version of the standard namedtuple collections.namedtuple with support for default values.

from __future__ import print_function

from namedtuplex.abc import NamedTupleXABC


class MyMixin(NamedTupleXABC):
    _fields = ('name2', 'name3',)  # chnages now to a non-abstract class
    _fielddefaults = (22, 33)


class MyClassABC(object):
    myvar = 4711

class MyClass(MyClassABC, MyMixin,):
    _fields = ('name0', 'name1',)  # chnages now to a non-abstract class


x = MyClass(11, 22,)

print(x)

5.3.4. Inheritance Parameters

The class NamedTupleXABC supports various parameters for the configuration of the class factory resulting in the inheritance behaviour.

_fields	field names
_fielddefaults	default values for fields
_merge	merge two objects
_module	for Python-3.6+
_rename	replace silently faulty names
_tuplefactory	alternative factory
_typename	name of type for created class
_verbose	raise display level

For details see The namedtuplex API.