python - 如何在 while 循环中使用 raw_input()

Question

只是尝试编写一个程序来接受用户输入并将其添加到“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

然而，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

我在这里缺少一些基本规则吗？

Answer 1

raw_input 返回一个字符串而不是整数:

所以，

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

使用int():

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

仅使用 if，如果您只从用户那里获取单个输入:

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