如何删除部分项目并替换循环中的列表元素？

Question

我做错了什么,这两个循环不起作用？链接是一个列表.

links = ['newarklongtermparking.com',
 'www.airportparkingreservations.com',
 'airparkparking.com',
 'jfklongtermparking.com',
 'book2park.com',
 'globalairportparking.com',
 'neworleansparking.com',
 'parkwayparking.com',
 'www.airportparkinginc.com',
 'airportparkfly.com',
 'unitedairportparking.com',
 'www.way.com',
 'cheapairportparking.org',
 'wallypark.com',
 'parkbytheports.com',
 'www.cheapparkfly.com']

删除www.

for a in links:
    if (a[0] == a[1] == a[2] == 'w'):
        a = a[4:]

添加正确的链接形式

for a in links:
    a = 'https://www.' + a

Answer 1

你正在做的是修改循环变量.这根本不会影响列表.如果你想修改元素,我建议使用enumerate,然后通过它们的索引访问列表项:

for i, a in enumerate(links):
    prefix = 'https://' if a.startswith('www') else 'https://www.'
    links[i] = prefix + a

处理完毕后,这就是links:

https://www.newarklongtermparking.com
https://www.airportparkingreservations.com
https://www.airparkparking.com
https://www.jfklongtermparking.com
https://www.book2park.com
https://www.globalairportparking.com
https://www.neworleansparking.com
https://www.parkwayparking.com
https://www.airportparkinginc.com
https://www.airportparkfly.com
https://www.unitedairportparking.com
https://www.way.com
https://www.cheapairportparking.org
https://www.wallypark.com
https://www.parkbytheports.com
https://www.cheapparkfly.com