python中[:]是什么意思
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What is the meaning of [:] in python
提问by Sourav
What does the line del taglist[:]do in the code below?
del taglist[:]下面的代码中的行有什么作用？
import urllib
from bs4 import BeautifulSoup
taglist=list()
url=raw_input("Enter URL: ")
count=int(raw_input("Enter count:"))
position=int(raw_input("Enter position:"))
for i in range(count):
print "Retrieving:",url
html=urllib.urlopen(url).read()
soup=BeautifulSoup(html)
tags=soup('a')
for tag in tags:
taglist.append(tag)
url = taglist[position-1].get('href', None)
del taglist[:]
print "Retrieving:",url
The question is "write a Python program that expands on http://www.pythonlearn.com/code/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". Sample problem: Start at http://python-data.dr-chuck.net/known_by_Fikret.htmlFind the link at position 3 (the first name is 1). Follow that link. Repeat this process 4 times. The answer is the last name that you retrieve. Sequence of names: Fikret Montgomery Mhairade Butchi Anayah Last name in sequence: Anayah
问题是“编写一个在http://www.pythonlearn.com/code/urllinks.py上扩展的 Python 程序。该程序将使用 urllib 从下面的数据文件中读取 HTML，从锚点中提取 href= vaues标签，扫描与列表中名字相关的特定位置的标签，点击该链接并重复该过程多次并报告您找到的姓氏”。示例问题：从http://python-data.dr-chuck.net/known_by_Fikret.html开始， 在位置 3（名字为 1）处找到链接。按照那个链接。重复此过程 4 次。答案是您检索到的姓氏。姓名顺序：Fikret Montgomery Mhairade Butchi Anayah 姓氏顺序：Anayah
回答by khazhyk
[:]is the array slice syntax for every element in the array.
[:]是数组中每个元素的数组切片语法。
This answer here goes more in depth of the general uses: Explain Python's slice notation
此处的答案更深入地介绍了一般用途：解释 Python 的切片符号
del arr # Deletes the array itself
del arr[:] # Deletes all the elements in the array
del arr[2] # Deletes the second element in the array
del arr[1:] # etc..
