python:我该如何做简单的变量声明？

Question

我的代码是测试我试图弄清楚为什么p & ~(p & (p - 1))不测试2的指数.无论如何,解释器in = 1因为某种原因不喜欢while循环之前.

码:

def getnumber(str):
    num=0
    for i in str:
        zz = ord(i)-48
        if zz<0 or zz>9:
            num=-1
            break
        else:
            num=(num*10)+zz
    return num

def testexp2(p):
    table = {1:1,2:2,4:3,8:4,16:5,32:6,64:7,128:8,256:9}
    if p & ~(p & (p - 1)):
        print "yes"
    else:
        print "no"


in = 1
while in is not -1:
    in = raw_input("> ")
    in = getnumber(in)
    if in>-1:
        testexp2(in)
    else:
        print "\nDone\n\n"

Answer 1

几个问题:

1. in 是python中的保留关键字,因此您不能将其用作变量名.
2. while inp is not -1应该是while inp != -1.(我用的是inp代替in)
3. 该getnumber功能可以简化为:

码:

def getnumber(strs):
    num = int(strs)
    return -1 if num < 0 else num