Callable dictionaries¶

class
sage.misc.callable_dict.
CallableDict
¶ Bases:
dict
Callable dictionary.
This is a trivial subclass of
dict
with an alternative view as a function.Typical use cases involve passing a dictionary \(d\) down to some tool that takes a function as input. The usual idiom in such use cases is to pass the
d.__getitem__
bound method. A pitfall is that this object is not picklable. When this feature is desired, aCallableDict
can be used instead. Note however that, with the current implementation,CallableDict
is slightly slower thand.__getitem__
(see trac ticket #6484 for benchmarks, and trac ticket #18330 for potential for improvement).EXAMPLES:
sage: from sage.misc.callable_dict import CallableDict sage: d = CallableDict({'one': 1, 'zwei': 2, 'trois': 3}) sage: d['zwei'] 2 sage: d('zwei') 2
In case the input is not in the dictionary, a
ValueError
is raised, for consistency with the function call syntax:sage: d[1] Traceback (most recent call last): .... KeyError: 1 sage: d(1) Traceback (most recent call last): .... ValueError: 1 is not in dict