i get this after everythin is done Key Error: "po5"

car={"po1":50,"po2":"-","po3":15,"po4":"+","po5":12}
vocar = list(car.keys())
inter=0
def cal(car,vocar,inter):
    while len(car)!=1:
        for inter in range(len(car)):
            if car.get(vocar[inter],0)=="+":
                new=car.get(vocar[inter-1])+car.get(vocar[inter+1])
                car.pop(vocar[inter])
                car.pop(vocar[inter+1])
                car.update({vocar[inter-1]:new})
                car1=car
                vocar1=list(car1.keys())
                inter1=0
                cal(car1,vocar1,inter1)
            elif car.get(vocar[inter],0)=="-":
                new=car.get(vocar[inter-1])-car.get(vocar[inter+1])
                car.pop(vocar[inter])
                car.pop(vocar[inter+1])
                car.update({vocar[inter-1]:new})
                car1=car
                vocar1=list(car1.keys())
                inter1=0
                cal(car1,vocar1,inter1)
    print(car)            
cal(car,vocar,inter)

i keep getting keyerror even if i get what i wanted which is {'po1': 47}

but after every thing is done gives key error please help i spent 2 days but #couldn't solve the problem