one more example with EventGenerator

dream/simulation/Examples/ChangingPredecessors.py

+from dream.simulation.imports import Machine, Queue, Exit, Part, EventGenerator, ExcelHandler  
+from dream.simulation.Globals import runSimulation, G
+
+
+# method that is to be invoked by the generator. 
+# it changes the predecessor of the Machine
+def changeMachinePredecessor(machine, possiblePredecessors):
+    # if the machine has no predecessors (at the start of the simulation)
+    # pick the first of the list
+    if not len(machine.previous):
+        machine.previous.append(possiblePredecessors[0])
+    # else loop through the possible predecessors and if one is not the current
+    # set this as predecessor and break
+    else:
+        for buffer in possiblePredecessors:
+            if not buffer==machine.previous[0]:
+                machine.previous[0]=buffer  
+                break  
+    # if canDispose is not triggered in the predecessor send it
+    if not machine.previous[0].canDispose.triggered:
+        machine.previous[0].canDispose.succeed()
+    print G.env.now, 'from now on the machine will take from', machine.previous[0].id
+        
+#define the objects of the model 
+Q1=Queue('Q1','Queue1', capacity=float('inf'))
+Q2=Queue('Q2','Queue2', capacity=float('inf'))
+M=Machine('M1','Machine', processingTime={'distributionType':'Fixed','mean':3})
+E=Exit('E1','Exit')  
+P1=Part('P1', 'Part1', currentStation=Q1)
+entityList=[]
+for i in range(5):      # create the WIP in a loop
+    Q1PartId='Q1_P'+str(i)
+    Q1PartName='Q1_Part'+str(i)
+    PQ1=Part(Q1PartId, Q1PartName, currentStation=Q1)
+    entityList.append(PQ1)
+    Q2PartId='Q2_P'+str(i)
+    Q2PartName='Q2_Part'+str(i)
+    PQ2=Part(Q2PartId, Q2PartName, currentStation=Q2)
+    entityList.append(PQ2)
+    
+#define predecessors and successors for the objects    
+Q1.defineRouting(successorList=[M])
+Q2.defineRouting(successorList=[M])
+M.defineRouting(successorList=[E])
+E.defineRouting(predecessorList=[M])
+
+EV=EventGenerator('EV', 'PredecessorChanger', start=0, stop=50, interval=10,method=changeMachinePredecessor, 
+                  argumentDict={'machine':M, 'possiblePredecessors':[Q1,Q2]})  
+
+def main():
+    # add all the objects in a list
+    objectList=[Q1,Q2,M,E,EV]+entityList  
+    # set the length of the experiment  
+    maxSimTime=float('inf')
+    # call the runSimulation giving the objects and the length of the experiment
+    runSimulation(objectList, maxSimTime, trace='Yes')
+    #print the results
+    print '='*50
+    print "the system produced", E.numOfExits, "parts in", E.timeLastEntityLeft, "minutes"
+    working_ratio = (M.totalWorkingTime/E.timeLastEntityLeft)*100
+    print "the total working ratio of the Machine is", working_ratio, "%"
+    ExcelHandler.outputTrace('ChangingPredecessors')
+    return {"parts": E.numOfExits,
+            "simulationTime":E.timeLastEntityLeft,
+          "working_ratio": working_ratio}
+
+if __name__ == '__main__':
+    main()
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