Question

print "HEllo !!"
print "Today, I will calculate something for you !!"#introduces itself 
inp = True
def start():
    print "type 1 for ADDITION"
    print "type 2 for SUBTRACTION"
    print "type 3 for MULTIPLICATION"      #asks for the kind of calculation 
    print "type 4 for DIVISION"
    press=int(raw_input())
    if press >= 5 :
            print "Choose a NUMBER which is less than 5 and you will get the answer!!"
            print "-------------------------------"
    if press == 1:
        print "Enter your first number"
        num1 = input()
        print "enter your second number"            #adds 
        num2 = input()
        result = num1 + num2
        print " Your answer is "+ str(result)
        print "-------------------------------"
    if press == 2 :
        print "Enter your first number"
        num1 = input()
        print "enter your second number"            #subtracts      
        num2 = input()
        result = num1 - num2
        print " Your answer is "+ str(result)
        print "-------------------------------"
    if press == 3:
        print "Enter your first number"
        num1 = input()
        print "enter your second number"
        num2 = input()                              #multiplies             
        result = num1 * num2
        print " Your answer is "+ str(result)
        print "-------------------------------"
    if press == 4:
        print "Enter your first number"
        num1 = input()                              #divides 
        print "enter your second number"
        num2 = input()
        result = num1/num2
        print " Your answer is "+ str(result)
        print "-------------------------------"
while inp : 
    start()

所以我使用基本命令创建了这个计算器，唯一的问题是当有人输入一个字母时，它要求1到4的数字，它会显示python错误。相反，我希望能够打印一个自定义的错误，例如＆＃34;只允许数字＆＃34;或类似的东西，而不是python显示的常规错误。我可以做什么改变，以便它接收数字和字母，但是当有人输入一封信时会显示一个定制的错误？附：：我要求var＆＃34;按＆＃34;而不是＆＃34; num1＆＃34;或＆＃34; num2＆＃34;

Answer 1

你可以这样做：

num1 = None
while num1 is None:
    try:
        num1 = int(num1)
    except ValueError:
        print "ERROR: Invalid Input"

这会尝试将输入转换为整数。如果没有这样做，那么＆＃34;中的代码除了＆＃34;部分将运行。

Answer 2

您可以使用str.isdigit()检查字符串是否只包含数字，如果是这种情况则返回true，如果字符串包含任何非数字字符，则返回false。

python：怎么收信？

2 个答案: