使用美丽的汤从未知页数中抓取数据

Question

I want to parse some info from website that has data spread among several pages.

The problem is I don't know how many pages there are. There might be 2, but there might be also 4, or even just one page.

How can I loop over pages when I don't know how many pages there will be?

I know however the url pattern which looks something like in the code below.

Also, the pages names are not plain numbers but they are in 'pe2' for page 2 and 'pe4' for page 3 etc. so can't just loop over range(number).

This dummy code for the loop I am trying to fix.

pages=['','pe2', 'pe4', 'pe6', 'pe8',]

import requests 
from bs4 import BeautifulSoup
for i in pages:
    url = "http://www.website.com/somecode/dummy?page={}".format(i)
    r = requests.get(url)
    soup = BeautifulSoup(r.content)
    #rest of the scraping code

Answer 1

You can use a while loop that will stop to run when encounters an exception.

Code:

from bs4 import BeautifulSoup
from time import sleep
import requests 

i = 0
while(True):
    try:
        if i == 0:
            url = "http://www.website.com/somecode/dummy?page=pe"
        else:
            url = "http://www.website.com/somecode/dummy?page=pe{}".format(i)
        r = requests.get(url)
        soup = BeautifulSoup(r.content, 'html.parser')

        #print page url
        print(url)

        #rest of the scraping code

        #don't overflow website
        sleep(2)

        #increase page number
        i += 2
    except:
        break

Output:

http://www.website.com/somecode/dummy?page
http://www.website.com/somecode/dummy?page=pe2
http://www.website.com/somecode/dummy?page=pe4
http://www.website.com/somecode/dummy?page=pe6
http://www.website.com/somecode/dummy?page=pe8
...
... and so on, until it faces an Exception.