Question

我正在抓取网页，并且每隔几秒就会更改某个变量minute。此minute位于永久运行的def内。如果，例如，minute == 80，if语句只运行一次，我怎么能这样做呢？

以下是代码的外观：

def login(): # necesarry for this
// stuff
return r

def run(r):
    //stuff
    minute_soup = soup.find_all("span", {"class":"clock-period"})
    minute = minute_soup[0].text

    if minute == 80:
        print(minute)

    time.sleep(10)

r = login()
while True:
   run(r)

目前，每次minute等于80时，它会一次又一次地做同样的事情，每隔10秒才会minute不等于80.有什么方法可以做minute等于80时的一次？

Answer 1

您可以使用该参数来保存标志：

def run(r):
    //stuff
    minute_soup = soup.find_all("span", {"class":"clock-period"})
    minute = minute_soup[0].text

    if minute == 80 and r.flag:
        r.flag = False
        print(minute)
    if minute != 80:
        r.flag = True

    time.sleep(10)

r = login()
r.flag = True
while True:
   run(r)

Answer 2

正如我从您的问题中所理解的，您可以使用from urllib.request import urlopen as uReq from bs4 import BeautifulSoup as soup my_url = 'https://www.realtor.ca/Residential/map.aspx#CultureId=1&ApplicationId=1&RecordsPerPage=9&MaximumResults=9&PropertySearchTypeId=1&TransactionTypeId=2&StoreyRange=0-0&BedRange=0-0&BathRange=0-0&NumberofDays=4&LongitudeMin=-122.8479843139653&LongitudeMax=-122.68181610107467&LatitudeMin=49.244425437286374&LatitudeMax=49.303560989620294&SortOrder=A&SortBy=1&viewState=l&Longitude=-122.76490020752&Latitude=49.2740020751953&CurrentPage=1&ZoomLevel=13&PropertyTypeGroupID=1' #opening up connection, grabbing the page uClient = uReq(my_url) page_content = uClient.read() uClient.close() #html parsing content_soup = soup(page_content, "html.parser")，当第一时间分钟变为flag时，将其设置为true，则80将永远不再执行：

if

Answer 3

这将是这样的：

flag = true
def run(r):
    if r == 80:
        if flag:
            flag = false
            //More stuff
    else:
        flag = true

我建议你研究一下事件处理，因为无限循环通常可以通过使用导致代码更清晰的事件来解决

Answer 4

minuteRunOnce = False
def run(r):
    //stuff
    minute_soup = soup.find_all("span", {"class":"clock-period"})
    minute = minute_soup[0].text

    if (minute == 80 and not(minuteRunOnce)):
        print(minute)
        minuteRunOnce = True

    time.sleep(10)

r = login()
while True:
   run(r)

如何在Python中只执行一次“if”语句？

4 个答案: