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August 19, 2020 15:27
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Simple memoizing DAG in Python using decorators
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| from functools import wraps | |
| from inspect import getmembers, ismethod | |
| class MemoizingDAG: | |
| def __init__(self, *args, **kwargs): | |
| super().__init__(*args, **kwargs) | |
| # memory of target results | |
| self._built_targets = {} | |
| # map target names to methods | |
| self._target_actors = {} | |
| for name, obj in getmembers(self): | |
| if (name.startswith('__') and name.endswith('__') | |
| or not ismethod(obj) | |
| or not hasattr(obj, 'target_name')): | |
| continue | |
| self._target_actors[getattr(obj, 'target_name')] = obj | |
| @staticmethod | |
| def register(name, *prerequisites): | |
| def wrapper(f): | |
| @wraps(f) | |
| def f_(self, *args, **kwargs): | |
| for req in prerequisites: | |
| self._target_actors[req](*args, **kwargs) | |
| # Return memoized result | |
| if name and name in self._built_targets: | |
| return self._built_targets[name] | |
| result = f(self, *args, **kwargs) | |
| # Memoize result | |
| if name: | |
| self._built_targets[name] = result | |
| return result | |
| # Dress method with target_name property | |
| f_.target_name = name | |
| return f_ | |
| return wrapper | |
| class Example(MemoizingDAG): | |
| def __init__(self): | |
| super().__init__() | |
| @MemoizingDAG.register('A') | |
| def mk_A(self): | |
| print('making A') | |
| return 'A' | |
| @MemoizingDAG.register('B', 'A') | |
| def mk_B(self): | |
| print('making B') | |
| return 'B' | |
| @MemoizingDAG.register('C', 'A', 'B') | |
| def mk_C(self): | |
| print('making C') | |
| return 'C' | |
| if __name__ == '__main__': | |
| print('Example 1') | |
| e1 = Example() | |
| print('mk_A') | |
| e1.mk_A() | |
| print('mk_B') | |
| e1.mk_B() | |
| print('mk_C') | |
| e1.mk_C() | |
| print() | |
| e2 = Example() | |
| print('Example 2') | |
| print('mk_C') | |
| e2.mk_C() |
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