beatifulsoup intro

Beautiful Soup 4 Python

Overview

This article is an introduction to BeautifulSoup 4 in Python.If you want to know more I recommend you to read the official documentationfound here.

What is Beautiful Soup?

Beautiful Soup is a Python library for pulling data out of HTML and XML files. 

BeautifulSoup 3 or 4?

Beautiful Soup 3 has been replaced by Beautiful Soup 4.Beautiful Soup 3 only works on Python 2.x, but Beautiful Soup 4 also works onPython 3.x. Beautiful Soup 4 is faster, has more features, and works with third-party parserslike lxml and html5lib. You should use Beautiful Soup 4 for all new projects.

Installing Beautiful Soup

If you run Debian or Ubuntu, you can install Beautiful Soup with the systempackage manager

apt-get install python-bs4

Beautiful Soup 4 is published through PyPi, so if you can’t install it with thesystem packager, you can install it with easy_install or pip. The package name is beautifulsoup4, and the same package works on Python 2 andPython 3.

easy_install beautifulsoup4pip install beautifulsoup4

If you don’t have easy_install or pip installed, you can download the BeautifulSoup 4 source tarball and install it with setup.py.python setup.py install

BeautifulSoup Usage

Right after the installation you can start using BeautifulSoup. At the beginning of your Python script, import the libraryNow you have to pass something to BeautifulSoup to create a soup object. That could be a document or an URL. BeautifulSoup does not fetch the web page for you, you have to do that yourself. That's why I use urllib2 in combination with the BeautifulSoup library.

Filtering

There are some different filters you can use with the search API. Below I will show you some examples on how you can pass those filters intomethods such as find_all You can use these filters based on a tag’s name, on its attributes, on the textof a string, or on some combination of these.

A string

The simplest filter is a string. Pass a string to a search method and Beautiful Soup will perform a match againstthat exact string. This code finds all the 'b' tags in the document (you can replace b with anytag you want to find)

soup.find_all('b')

If you pass in a byte string, Beautiful Soup will assume the string is encodedas UTF-8. You can avoid this by passing in a Unicode string instead.

A regular expression

If you pass in a regular expression object, Beautiful Soup will filter againstthat regular expression using its match() method. This code finds all the tags whose names start with the letter "b",in this case, the 'body' tag and the 'b' tag:

import refor tag in soup.find_all(re.compile("^b")):    print(tag.name)

This code finds all the tags whose names contain the letter "t":

for tag in soup.find_all(re.compile("t")):    print(tag.name)

A list

If you pass in a list, Beautiful Soup will allow a string match against anyitem in that list. This code finds all the 'a' tags and all the 'b' tags

print soup.find_all(["a", "b"])

True

The value True matches everything it can. This code finds all the tags in the document, but none of the text strings:

for tag in soup.find_all(True):    print(tag.name)

A function

If none of the other matches work for you, define a function that takes anelement as its only argument. Please see the official documentation if you want to do that. 

BeautifulSoup Object

As an example, we'll use the very website you currently are on (http://www.pythonforbeginners.com)To parse the data from the content, we simply create a BeautifulSoup object for itThat will create a soup object of the content of the url we passed in. From this point, we can now use the Beautiful Soup methods on that soup object.We can use the prettify method to turn a BS parse tree into a nicely formattedUnicode string

The Find_all method

The find_all method is one of the most common methods in BeautifulSoup. It looks through a tag’s descendants and retrieves all descendants that matchyour filters. 

soup.find_all("title")soup.find_all("p", "title")soup.find_all("a")soup.find_all(id="link2")

Let's see some examples on how to use BS 4

from bs4 import BeautifulSoupimport urllib2url = "http://www.pythonforbeginners.com"content = urllib2.urlopen(url).read()soup = BeautifulSoup(content)print soup.prettify()print title>> 'title'? Python For Beginnersprint soup.title.string>> ? Python For Beginnersprint soup.p 
print soup.aPython For Beginners

Navigating the Parse Tree

If you want to know how to navigate the tree please see the official documentationThere you can read about the following things:Going down        Navigating using tag names        .contents and .children        .descendants        .string        .strings and stripped_stringsGoing up        .parent        .parentsGoing sideways        .next_sibling and .previous_sibling        .next_siblings and .previous_siblingsGoing back and forth        .next_element and .previous_element        .next_elements and .previous_elements

Extracting all the URLs found within a page 'a' tags

One common task is extracting all the URLs found within a page’s 'a' tagsUsing the find_all method, gives us a whole list of elements with the tag "a". 

for link in soup.find_all('a'):    print(link.get('href'))

Output:

..http://www.pythonforbeginners.com..http://www.pythonforbeginners.com/python-overview-start-here/..http://www.pythonforbeginners.com/dictionary/..http://www.pythonforbeginners.com/python-functions-cheat-sheet/..http://www.pythonforbeginners.com/lists/python-lists-cheat-sheet/..http://www.pythonforbeginners.com/loops/..http://www.pythonforbeginners.com/python-modules/..http://www.pythonforbeginners.com/strings/..http://www.pythonforbeginners.com/sitemap/......

Extracting all the text from a page

Another common task is extracting all the text from a page:

print(soup.get_text())

Output:

Python For BeginnersPython BasicsDictionaryFunctionsListsLoopsModulesStringsSitemap......

Get all links from Reddit

As a last example, let's grab all the links from Reddit

from bs4 import BeautifulSoupimport urllib2redditFile = urllib2.urlopen("http://www.reddit.com")redditHtml = redditFile.read()redditFile.close()soup = BeautifulSoup(redditHtml)redditAll = soup.find_all("a")for links in soup.find_all('a'):    print (links.get('href'))

Output:

#content..http://www.reddit.com/r/AdviceAnimals/..http://www.reddit.com/r/announcements/..http://www.reddit.com/r/AskReddit/..http://www.reddit.com/r/atheism/..http://www.reddit.com/r/aww/..http://www.reddit.com/r/bestof/..http://www.reddit.com/r/blog/..http://www.reddit.com/r/funny/..http://www.reddit.com/r/gaming/..http://www.reddit.com/r/IAmA/..http://www.reddit.com/r/movies/..http://www.reddit.com/r/Music/..http://www.reddit.com/r/pics/..http://www.reddit.com/r/politics/...