Day21_Part01.py

operators = {'+': lambda a, b: a + b,
             '-': lambda a, b: a - b,
             '*': lambda a, b: a * b,
             '/': lambda a, b: a // b,
             }

with open("Input_Day21.txt") as f:
    raw_data = [x.strip() for x in f]

d = []
for row in raw_data:
    id, op = row.split(": ")
    d.append((id, op))

monkeys = {}
while 'root' not in monkeys:
    for _m,_d in d:
        if _m in monkeys:
            continue
        if _d.isnumeric():
            monkeys[_m] = int(_d)
        else:
            m1, op, m2 = _d.split(' ')
            if (m1 in monkeys) and (m2 in monkeys):
                monkeys[_m] = operators[op](monkeys[m1], monkeys[m2])
print(monkeys['root'])