On 05/18/2015 04:48 PM, Carsten Knoll wrote:
> On 05/18/2015 04:12 PM, Amit Saha wrote:
>> On Mon, May 18, 2015 at 11:56 PM, Carsten Knoll <[email protected]> wrote:
>>> I want to equip an Symbol with an additional attribute to store some
>>> specific information right in place.
>
> Equipping that class with new methods or class variables is no problem
> but adding instance attributes is not possible. Not sure where this
> behavior is implemented.
>
If someone is interested: I found an (ugly) workaround:
# because sympy does not allow to dynamically attach attributes
# to symbols we set up our own infrastructure for storing them
import sympy as sp
sp._attribute_store = {}
def new_setattr(self, name, value):
try:
self.__orig_setattr__(name, value)
except AttributeError:
sp._attribute_store[(self, name)] = value
def new_getattr(self, name):
try:
res = self.__getattribute__(name)
except AttributeError, AE:
try:
res = sp._attribute_store[(self, name)]
except KeyError:
# raise the original AttributeError
raise AE
return res
sp.Symbol.__orig_setattr__ = sp.Symbol.__setattr__
sp.Symbol.__setattr__ = new_setattr
sp.Symbol.__getattr__ = new_getattr
Still, I would prefer to store the attribute directly 'inside' the
symbol instance but at least in the rest of my code this solution feel
like it were like that.
Carsten.
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