def __enter__(self):
"""Record all future changes to the model, undoing them when a call to
__exit__ is received"""
# Create a new context and add it to the stack
try:
self._contexts.append(HistoryManager())
except AttributeError:
self._contexts = [HistoryManager()]
return self
def __init__(self, model):
self.history_manager = None
self._model = model
self.variables = {}
self.constraints = {}
self.objective = None
self.original_objective = model.solver.objective
self._contexts = [HistoryManager()]
self.transaction_id = None
def reset(self):
"""
Removes all constraints and variables from the cache.
"""
variables = list(self.variables.keys())
constraints = list(self.constraints.keys())
while len(self._contexts) > 0:
manager = self._contexts.pop()
manager.reset()
self._contexts.append(HistoryManager())
assert all(var_id not in self._model.solver.variables for var_id in variables)
assert all(const_id not in self._model.solver.constraints for const_id in constraints)
self.variables = {}
self.constraints = {}
self._model.objective = self.original_objective
self.objective = None
def begin_transaction(self):
"""
Creates a time point. If rollback is called, the variables and constrains will be reverted to this point.
"""
self._contexts.append(HistoryManager())