Calc from sir

def check_value(num):
    try:
        num = float(num)
        return True, num
    except ValueError:
        print("invalid data") 
        return False,
def check_op(operator):    
    if operator in ['+', '-', '*', '/']:
        return True
    else:
        return False  
def calc(v1,v2,oper):          
    if v1[0] and v2[0] and oper:
        if op == "+":
            result = v1[1] + v2[1]
        if op == "-":
            result = v1[1] - v2[1]
        if op == "*":
            result = v1[1] * v2[1]
        if op == "/":
            if v2[1] == 0:
                result = False
            else:    
                result = v1[1] / v2[1]           
        print(result)
        return result
    else:
        print("wrong expression") 
        return False  
exp = input("please input expression with spaces : ")
ls = exp.split()
while len(ls) >= 3 and len(ls) % 2:
    x = ls[0]
    y = ls[2]
    op =ls[1]        
    result = calc(check_value(x),check_value(y),check_op(op))
    if result != False:
        del ls[:2]
        ls[0] = result
    else:
        break