如何将原始输入（）与while循环一起使用

Question

只是想写一个程序，接受用户的输入并将其添加到“数字”列表中：

print "Going to test my knowledge here"
print "Enter a number between 1 and 20:"

i = raw_input('>> ')
numbers = []

while 1 <= i <= 20 :
    print "Ok adding %d to numbers set: " % i 
    numbers.append(i)

    print "Okay the numbers set is now: " , numbers

但是，当我执行程序时，它只运行到raw_input（）

Going to test my knowledge here
Enter a number between 1 and 20:
>>> 4

我有没有遗漏一些基本原则？？

Answer 1

raw_input返回的字符串不是整数：

所以

>>> 1 <= "4" <= 20
False

使用int()：

i = int(raw_input('>> '))

如果只接受用户的一个输入，请使用if：

if 1 <= i <= 20 :
    print "Ok adding %d to numbers set: " % i 
    numbers.append(i)

    print "Okay the numbers set is now: " , numbers

对多个输入使用while：

i = int(raw_input('>> '))
numbers = []

while 1 <= i <= 20 :
    print "Ok adding %d to numbers set: " % i 
    numbers.append(i)
    i = int(raw_input('>> '))                   #asks for input again
print "Okay the numbers set is now: " , numbers