Python 2.7 为什么不是'；我的程序运行不正常吗？if语句不是'；t被求值，它直接跳转到Python中的else语句

当我试图将任何值输入op时，总是执行else语句

这里有什么问题？我是编程新手

print "Basic Calculator"
print "Options:"
print "For addition, type add"
print "For subtraction, type sub"
print "For multiplication, type mul"
print "For division, type div"

op = raw_input()
num1 = raw_input("Enter first number: ")
num2 = raw_input("Enter second number: ")

if op == 'sum':
    print "The sum is: ", num1 + num2
elif op == 'sub':
    if num1 > num2:
        print "The subtraction is: ", num1 - num2
    else:
        print "The subtraction is: ", num1 - num2
elif op == 'mul':
    print "The product is: ", num1 * num2
elif op == 'div':
    print "The division is: ", num1 / num2
else:
    print "You entered an incorrect operation"

---

如果先键入所需的操作，然后键入两个数字，则可以正常工作，还需要将数字转换为整数：

print "Basic Calculator"
print "Options:"
print "For addition, type add"
print "For subtraction, type sub"
print "For multiplication, type mul"
print "For division, type div"

op = raw_input("Enter the operation wanted (add, sub, mul, div): ")
num1 = raw_input("Enter first number: ")
num2 = raw_input("Enter second number: ")

intNum1 = int(num1)
intNum2 = int(num2)
if op == 'sum':
    print "The sum is: ", intNum1 + intNum2
elif op == 'sub':
    if intNum1 > intNum2:
        print "The subtraction is: ", intNum1 - intNum2
    else:
        print "The subtraction is: ", intNum1 - intNum2
elif op == 'mul':
    print "The product is: ", intNum1 * intNum2
elif op == 'div':
    print "The division is: ", intNum1 / intNum2
else:
    print "You entered an incorrect operation"

---

它非常适合我：）除了类型转换之外，我在这里没有看到任何问题。提供您提供的输入和相应的输出。您如何证明等式运算未被计算？我的意思是，通常这需要添加一个函数，即

def compare（val，target）：打印“比较%r和%r”%（val，target）；return val==target

然后将该函数放入

if

语句中并查找副作用（print语句）。顺便说一句，

print“您输入的操作不正确：%r”%（op，）

将更容易诊断早期比较失败的原因。