无捕获分组

当你要将一部分规则作为一个整体对它进行某些操作，比如指定其重复次数时，你需要将这部分规则用

(?:)

把它包围起来。

分支条件

在正则表达式中，分支条件是一个很常用的条件。

满足条件A 或者 满足条件B  ，这个时候我们就可以使用分支条件了。

分支条件使用的符号为 

|

 

 

代码示例：

我们突然发现，它把字符串分割成两个部分了

I have a dog  和  cat    而不是    I have a dog  和   I have a cat

如果我们只要区分dog和cat呢？正则要怎么写？我添加一个括号试试

还是不对，前面的 “I have a ”根本没有匹配

正确的写法是应该使用无捕获分组

 

 

来个高级一点的

import requestsimport reurl = "https://docs.djangoproject.com/en/1.6/intro/tutorial02/"res = requests.get(url)html = res.content# 捕获html中的 href 和 src 后的内容lines =  re.findall("(?:(?<=href=\")|(?<=src=\"))(?:(?:ht|f)tp[s]?)?.*?(?=\")",html,re.S)for line in lines:    print line

匹配结果如下：

root@kali:/recall/code# python re.py

/s/css/base.de56b042ddc0.css

/s/css/print.ac134bbb8dfc.css

/s/css/docs/docs.0047ef2d621d.css

/s/css/pygments.0d57d48be058.css

https://www.djangoproject.com/

/s/img/site/hdr_logo.b19c5e60269d.gif

https://www.djangoproject.com/

https://www.djangoproject.com/download/

https://docs.djangoproject.com/en/1.6/

https://www.djangoproject.com/weblog/

https://www.djangoproject.com/community/

https://code.djangoproject.com/

/en/1.6/

/en/1.2/intro/tutorial02/

/en/1.3/intro/tutorial02/

/en/1.4/intro/tutorial02/

/en/1.5/intro/tutorial02/

/en/1.7/intro/tutorial02/

/en/dev/intro/tutorial02/

#writing-your-first-django-app-part-2

../tutorial01/

#start-the-development-server

http://127.0.0.1:8000/admin/

../../_images/admin01.png

../../topics/i18n/translation/

#enter-the-admin-site

../../topics/auth/default/#topics-auth-creating-superusers

../../_images/admin02t.png

../../topics/auth/#module-django.contrib.auth

#make-the-poll-app-modifiable-in-the-admin

#explore-the-free-admin-functionality

../../_images/admin03t.png

../../_images/admin04t.png

../../_images/admin05t.png

../../ref/models/fields/#django.db.models.DateTimeField

../../ref/models/fields/#django.db.models.CharField

../../ref/models/fields/#django.db.models.DateTimeField

../../ref/settings/#std:setting-TIME_ZONE

../../_images/admin06t.png

#customize-the-admin-form

../../_images/admin07.png

../../_images/admin08t.png

../../_images/admin09.png

#adding-related-objects

../../_images/admin10.png

../../ref/models/fields/#django.db.models.ForeignKey

../../_images/admin11t.png

../../_images/admin15t.png

../../_images/admin12t.png

#customize-the-admin-change-list

../../_images/admin04t.png

../../_images/admin13t.png

../../_images/admin14t.png

../../ref/models/fields/#django.db.models.DateTimeField

#customize-the-admin-look-and-feel

#customizing-your-project-s-templates

../../ref/settings/#std:setting-TEMPLATE_DIRS

../../ref/settings/#std:setting-TEMPLATE_DIRS

#customizing-your-application-s-templates

../../ref/settings/#std:setting-TEMPLATE_DIRS

../../ref/templates/api/#template-loaders

#customize-the-admin-index-page

../../ref/settings/#std:setting-INSTALLED_APPS

../tutorial03/

../tutorial01/

../tutorial03/

/en/1.6/faq/

http://groups.google.com/group/django-users/

http://groups.google.com/group/django-users/

irc://irc.freenode.net/

http://django-irc-logs.com/

https://code.djangoproject.com/newticket?component=Documentation

#

#start-the-development-server

#enter-the-admin-site

#make-the-poll-app-modifiable-in-the-admin

#explore-the-free-admin-functionality

#customize-the-admin-form

#adding-related-objects

#customize-the-admin-change-list

#customize-the-admin-look-and-feel

#customizing-your-project-s-templates

#customizing-your-application-s-templates

#customize-the-admin-index-page

../tutorial01/

../tutorial03/

/en/1.6/contents/

/en/1.6/genindex/

/en/1.6/py-modindex/

/en/1.6/

../

/m/docs/django-docs-1.6-en.zip

http://media.readthedocs.org/pdf/django/1.6.x/django.pdf

http://media.readthedocs.org/epub/django/1.6.x/django.epub

http://readthedocs.org/

https://www.djangoproject.com/foundation/

https://www.djangoproject.com/trademarks/

http://mediatemple.net/

//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js

欢迎拍砖。