Source code for attributes

##  This file is part of pyFormex 2.0  (Mon Sep 14 12:29:05 CEST 2020)
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This module defines a general class for adding extra attributes to
other objects without cluttering the name space.

from pyformex.mydict import Dict

[docs]class Attributes(Dict): """A general class for holding attributes. This class is a versatile :term:`Mapping` class for objects that need a customizable set of attributes, while avoiding a wildly expanding name space. The class derives from :class:`Dict` and therefore has key lookup via normal dict key mechanism or via attribute syntax or via function call. It also provides a default_factory to lookup missing keys. The difference with the :class:`Dict` class are: - The function call can also be used to populate or update the contents of the Mapping. - By default, a default_factory is set returning None for any missing key. - Giving an attribute the value None removes it from the Mapping. Parameters ---------- default_factory: callable, optional If provided, missing keys will be looked up by a call to the default_factory. args, kargs: other positional and keyword arguments Any other arguments are passed to the dict initialization. Notes ----- While setting a single item to None will remove the item from the Attributes, None values can be entered using the update() method. The parameter order is different from previous implementation of this class. This was done for consistency with the Dict and CDict classes. Examples -------- >>> A = Attributes() >>> A Attributes({}) >>> A(color='red',alpha=0.7,ontop=True) >>> A Attributes({'color': 'red', 'alpha': 0.7, 'ontop': True}) >>> A['alpha'] = 0.8 >>> A.color = 'blue' >>> A.ontop = None # remove 'ontop' >>> A Attributes({'color': 'blue', 'alpha': 0.8}) >>> A = Attributes({'alpha': 0.8, 'color': 'blue'}) >>> A.ontop is None True Create another Attributes with A as default, override color: >>> B = Attributes(default_factory=A, color='green') >>> B Attributes({'color': 'green'}) >>> B.color, B.alpha # alpha found in A ('green', 0.8) >>> A.clear() >>> A Attributes({}) >>> A['alpha'], A.alpha, A('alpha') # all mechanisms still working (None, None, None) >>> B['alpha'], B.alpha, B('alpha') (None, None, None) >>> B(color=None,alpha=1.0) # remove and change in 1 operation >>> B Attributes({'alpha': 1.0}) >>> B.update(color=None) # update can be used to enter None values. >>> B Attributes({'alpha': 1.0, 'color': None}) >>> B['alpha'] = None >>> B Attributes({'color': None}) """ def __init__(self, default_factory=Dict.returnNone, *args, **kargs): if default_factory is None or callable(default_factory): pass elif len(args) == 0: args = [default_factory] default_factory = Dict.returnNone Dict.__init__(self, default_factory, *args, **kargs) # with args: key lookup # with kargs: set values def __call__(self, *args, **kargs): if len(args) > 0: return self[args[0]] else: for k in kargs: setattr(self, k, kargs[k]) # Remove items when value is set to None def __setitem__(self, key, value): if value is None: if key in self: del self[key] else: Dict.__setitem__(self, key, value) __setattr__ = __setitem__
# End