I get Key Error: "po5" after everything is done - python-3.x

Question

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 a key error even if I get what I wanted, which is {'po1': 47}.
But after everything is done, it gives me a key error. Please help!

Answer 1

At first:
while len(car)!=1
You pop item from car and try to make a recursion function then you can use:
if not car:
return
for inter in range(len(car)):
# ....
When you make a loop like this:
for inter in range(len(car))
that means:
| loop | inter |
|:----:|:-----:|
| 1 | 0 | car => [X, X, X ,X ,X]
| 2 | 1 | car => [X, X, X ,X]
| 3 | 2 | car => [X, X, X] ! ERR !
| 4 | 3 |
| 5 | 4 |
in loop 3 you have an error (maybe ;))
you can use the main dict:
for inter in car:
According above, You didn't need vocar anymore:
if car.get(inter,0)=="+":
"po1" is str and "po2" is int then you can't use + operator between int and int.
dictionaries are unordered
That means, every time you run it, item arrangments may be changed! so I change it:
car = [("po1",50), ("po2","-"),("po3",15),("po4","+"),("po5",12)]
We changed car then we can do this:
if inter[1] == "+":
car[head-1] = (inter[0], car[head-1][1]+car[head+1][1])
finally, we MUST remove car[head+1] at first and then remove car[inter].
car = [("po1",50), ("po2","-"),("po3",15),("po4","+"),("po5",12)]
def cal(car):
head = 0
if not car:
return
for inter in car:
if inter[1] == "+":
car[head-1] = (inter[0], car[head-1][1]+car[head+1][1])
car.remove(car[head+1])
car.remove(inter)
cal(car)
elif inter[1] =="-":
car[head-1] = (inter[0], car[head-1][1]-car[head+1][1])
car.remove(car[head+1])
car.remove(inter)
cal(car)
head += 1
return car[0][1]
print(cal(car))
OUT:
===
47