Typed#

class ubermagutil.typesystem.Typed(name=None, **kwargs)#

Descriptor allowing setting attributes only with values of a certain type.

Parameters:

  • expected_type (type) – Allowed type of value.

  • allow_none (bool) – If True, the value can be set with None.

Raises:

TypeError – If type(value) != expected_type.

Example

  1. Usage of Typed descriptor.

>>> import ubermagutil.typesystem as ts
...
>>> @ts.typesystem(myattribute=ts.Typed(expected_type=str))
... class DecoratedClass:
...     def __init__(self, myattribute):
...         self.myattribute = myattribute
...
>>> dc = DecoratedClass(myattribute='Nikola Tesla')
>>> dc.myattribute
'Nikola Tesla'
>>> dc.myattribute = 'Mihajlo Pupin'  # valid set
>>> dc.myattribute
'Mihajlo Pupin'
>>> dc.myattribute = 3.14  # invalid set
Traceback (most recent call last):
   ...
TypeError: ...

Note

This class was derived from ubermagutil.typesystem.Descriptor and inherits its functionality.

See also

Descriptor

Methods

__delete__

Deleting the decorated class attribute is never allowed and AttributeError is raised.

__dir__

Default dir() implementation.

__eq__

Return self==value.

__repr__

Return repr(self).

__set__

If self.const=True, changing the value of a decorated class attribute after the initial set is not allowed.
__set__(instance, value)#

If self.const=True, changing the value of a decorated class attribute after the initial set is not allowed.

Raises:

AttributeError – If changing the value of a decorated class attribute is attempted.

Example

  1. Changing the value of a constant decorated class attribute.

>>> import ubermagutil.typesystem as ts
...
>>> @ts.typesystem(myattribute=ts.Descriptor(const=True))
... class DecoratedClass:
...     def __init__(self, myattribute):
...         self.myattribute = myattribute
...
>>> dc = DecoratedClass(myattribute="John Doe")
>>> dc.myattribute
'John Doe'
>>> dc.myattribute = 'Jane Doe'
Traceback (most recent call last):
   ...
AttributeError: ...