这段代码中if语句哪里有问题？

Question

这段代码中，当visits的值为1时，为啥执行的还是visits>=4的while循环函数？

代码在这儿：

i = 1
while i == 1:
    printSiteInfo()
    global visits
    
    if visits == 0:
        GPIO.output(R,0)
        GPIO.output(Y,0)
        GPIO.output(G,0)
        
    if visits == 1:
        GPIO.output(R,1)
        GPIO.output(Y,0)
        GPIO.output(G,0)

    if visits == 2:
        GPIO.output(R,1)
        GPIO.output(Y,1)
        GPIO.output(G,0)

    if visits == 3:
        GPIO.output(R,1)
        GPIO.output(Y,1)
        GPIO.output(G,1)

    if visits >= 4:
        t = 0
        while(t <= visits):
            GPIO.output(R,0)
            GPIO.output(Y,0)
            GPIO.output(G,0)

            time.sleep(0.5)

            GPIO.output(R,1)
            GPIO.output(Y,1)
            GPIO.output(G,1)

            time.sleep(0.1)

            t = t + 1

    time.sleep(20)

Answer 1

代码不全，看不出问题所在。

我还想问执行了 visits >= 4 分支，那 visits == 1 分支执行了没有？

有一个简单的办法，你在前面增加加 print 语句打印 visits 的值，就能清晰的看到结果了。

i = 1
while i == 1:
    printSiteInfo()
    global visits
    print('i=', i, 'visits=', visits, 'id(visits)', id(visits))
    if visits == 0:
        print('in==0', 'i=', i, 'visits=', visits, 'id(visits)', id(visits))
        GPIO.output(R,0)
        GPIO.output(Y,0)
        GPIO.output(G,0)
        
    if visits == 1:
        print('in==1', 'i=', i, 'visits=', visits, 'id(visits)', id(visits))
        GPIO.output(R,1)
        GPIO.output(Y,0)
        GPIO.output(G,0)

    if visits == 2:
        print('in==2', 'i=', i, 'visits=', visits, 'id(visits)', id(visits))
        GPIO.output(R,1)
        GPIO.output(Y,1)
        GPIO.output(G,0)

    if visits == 3:
        print('in==3', 'i=', i, 'visits=', visits, 'id(visits)', id(visits))
        GPIO.output(R,1)
        GPIO.output(Y,1)
        GPIO.output(G,1)

    if visits >= 4:
        print('in>=4', 'i=', i, 'visits=', visits, 'id(visits)', id(visits))
        t = 0
        while(t <= visits):
            GPIO.output(R,0)
            GPIO.output(Y,0)
            GPIO.output(G,0)

            time.sleep(0.5)

            GPIO.output(R,1)
            GPIO.output(Y,1)
            GPIO.output(G,1)

            time.sleep(0.1)

            t = t + 1

    time.sleep(20)

根据输出结果再分析

Answer 2

第4行代码

global visits

你使用了global 用的是上方的visits 值可能为 4

例子如下：

c = 1 # global variable

def add():
    print(c)

add()

打印出来的结果是 1

Answer 3

用continue：

i = 1
while i == 1:
    printSiteInfo()
    global visits
    
    if visits == 0:
        # ...
        continue
        
    if visits == 1:
        # ...
        continue