目前在Coursera上自学Python网络爬虫。
写作业的时候碰到一个题目，就是要根据使用者输入的position，
搜寻网页中使用者指定position的网址，进入该网址后，
再搜寻下一页面中该指定position的网址，如此重复counter次
原始题目叙述为：
In this assignment you will write a Python program that expands on
http://www.py4e.com/code3/urllinks.py. The program will use urllib to read
the HTML from the data files below, extract the href= vaues from the anchor
tags, scan for a tag that is in a particular position relative to the first
name in the list, follow that link and repeat the process a number of times
and report the last name you find.
下面是我目前写好的部分，但只能打印出第一层指定位置的网址，不知道该怎么
依照指定的counter重复进入该网址再打印下几层的网址，请大家协助解惑了
import urllib.request, urllib.parse, urllib.error
from bs4 import BeautifulSoup
import ssl
# Ignore SSL certificate errors
ctx = ssl.create_default_context()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE
url = 'http://py4e-data.dr-chuck.net/known_by_Fikret.html'
counter = input ('Enter counter: ')
position = input ('Enter position: ' )
html = urllib.request.urlopen(url, context=ctx).read()
soup = BeautifulSoup(html, 'html.parser')
# Retrieve all of the anchor tags
tags = soup('a')
lst = []
for tag in tags:
link = tag.get('href', None)
lst.append(link)
print(lst[int(position)-1])