HTTP – Python Tutorial

HTTP – Parse HTML and XHTML

In this article you will learn how to parse the HTML (HyperText Mark-up Language) of a website. There are several Python libraries to achieve that. We will give a demonstration of a few popular ones.

Beautiful Soup – a python package for parsing HTML and XML
This library is very popular and can even work with malformed markup. To get the contents of a single div, you can use the code below:

from BeautifulSoup import BeautifulSoup
import urllib2
 
 
# get the contents
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
html = response.read()
 
parsed_html = BeautifulSoup(html)
print parsed_html.body.find('div', attrs={'class':'toc'})

This will output the HTML code of within the div called ‘toc’ (table of contents) of the wikipedia article. If you want only the raw text use:

print parsed_html.body.find('div', attrs={'class':'toc'}).text

If you want to get the page title, you need to get it from the head section:

print parsed_html.head.find('title').text

To grab all images URLs from a website, you can use this code:

from BeautifulSoup import BeautifulSoup
import urllib2
 
url = 'http://www.arstechnica.com/'
data = urllib2.urlopen(url).read()
soup = BeautifulSoup(data)
links = soup.findAll('img', src=True)
 
for link in links:
    print(link["src"])

To grab all URLs from the webpage, use this:

from BeautifulSoup import BeautifulSoup
import urllib2
 
url = 'http://www.arstechnica.com/'
data = urllib2.urlopen(url).read()
soup = BeautifulSoup(data)
links = soup.findAll('a')
 
for link in links:
    print(link["href"])

PyQuery – a jquery like library for Python
To extract data from the tags we can use PyQuery. It can grab the actual text contents and the html contents, depending on what you need. To grab a tag you use the call pq(‘tag’).

from pyquery import PyQuery    
import urllib2
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
 
html = response.read()
pq = PyQuery(html)
tag = pq('div#toc')
 
# print the text of the div
print tag.text()
 
# print the html of the div
print tag.html()

To get the title simply use:

tag = pq('title')

HTMLParser – Simple HTML and XHTML parser
The usage of this library is very different. With this library you have to put all your logic in the WebParser class. A basic example of usage below:

from HTMLParser import HTMLParser
import urllib2
 
# create parse
class WebParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print "Tag: " + tag
 
# get the contents
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
html = response.read()
 
# instantiate the parser and fed it some HTML
parser = WebParser()
parser.feed(html)

HTTP download file with Python

The urllib2 module can be used to download data from the web (network resource access). This data can be a file, a website or whatever you want Python to download. The module supports HTTP, HTTPS, FTP and several other protocols.

In this article you will learn how to download data from the web using Python.

Related courses

Download text

To download a plain text file use this code:

import urllib2
response = urllib2.urlopen('https://wordpress.org/plugins/about/readme.txt')
data = response.read()
print(data)

We get a response object using the urllib2.urlopen() method, where the parameter is the link. All of the file contents is received using the response.read() method call. After calling this, we have the file data in a Python variable of type string.

Download HTML

This will request the html code from a website. It will output everything to the screen.

import urllib2
response = urllib2.urlopen('http://en.wikipedia.org/')
html = response.read()
print html

Download file using Python

You can save the data to disk very easily after downloading the file:

import urllib2
response = urllib2.urlopen('https://wordpress.org/plugins/about/readme.txt')
data = response.read()
 
# Write data to file
filename = "test.txt"
file_ = open(filename, 'w')
file_.write(data)
file_.close()

The first part of the code downloads the file contents into the variable data:

import urllib2
response = urllib2.urlopen('https://wordpress.org/plugins/about/readme.txt')
data = response.read()

The second part stores it into a file (this file does not need to have the same filename)

# Write data to file
filename = "test.txt"
file_ = open(filename, 'w')
file_.write(data)
file_.close()

The ‘w’ parameter creates the file (or overwrites if it exists). You can read more about writing files here.

Requests: HTTP for Humans

If you want to request data from webservers, the traditional way to do that in Python is using the urllib library. While this library is effective, you could easily create more complexity than needed when building something. Is there another way?

Requests is an Apache2 Licensed HTTP library, written in Python. It’s powered by httplib and urllib3, but it does all the hard work for you.

To install type:

git clone https://github.com/kennethreitz/requests.git
cd requests
sudo python setup.py install

The Requests library is now installed. We will list some examples below:

Grabbing raw html using HTTP/HTTPS requests
We can now query a website as :

import requests
r = requests.get('http://pythonspot.com/')
print r.content

Save it and run with:

python website.py

It will output the raw HTML code.

Download binary image using Python

from PIL import Image
from StringIO import StringIO
import requests
 
r = requests.get('http://1.bp.blogspot.com/_r-MQun1PKUg/SlnHnaLcw6I/AAAAAAAAA_U$
i = Image.open(StringIO(r.content))
i.show()

An image retrieved using python

Website status code (is the website online?)

import requests
r = requests.get('http://pythonspot.com/')
print r.status_code

This returns 200 (OK). A list of status codes can be found here: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

Retrieve JSON from a webserver
You can easily grab a JSON object from a webserver.

import requests
 
import requests
r = requests.get('https://api.github.com/events')
print r.json()

HTTP Post requests using Python

from StringIO import StringIO
import requests
 
payload = {'key1': 'value1', 'key2': 'value2'}
r = requests.post("http://httpbin.org/post", data=payload)
print(r.text)

SSL verification, verify certificates using Python

from StringIO import StringIO
import requests
print requests.get('https://github.com', verify=True)

Extract data from the HTTP response header
With every request you send to a HTTP server, the server will send you some additional data. You can get extract data from an HTTP response using:

#!/usr/bin/env python
import requests
r = requests.get('http://pythonspot.com/')
print r.headers

This will return the data in JSON format. We can parse the data encoded in JSON format to a Python dict.

#!/usr/bin/env python
import requests
import json
r = requests.get('http://pythonspot.com/')
 
jsondata = str(r.headers).replace('\'','"')
headerObj = json.loads(jsondata)
print headerObj['server']
print headerObj['content-length']
print headerObj['content-encoding']
print headerObj['content-type']
print headerObj['date']
print headerObj['x-powered-by']

Extract data from HTML response
Once you get the data from a server, you can parse it using python string functions or use a library. BeautifulSoup is often used. An example code that gets the page title and links:

from bs4 import BeautifulSoup
import requests
 
# get html data
r = requests.get('http://stackoverflow.com/')
html_doc = r.content
 
# create a beautifulsoup object
soup = BeautifulSoup(html_doc)
 
# get title
print soup.title
 
# print all links
for link in soup.find_all('a'):
    print(link.get('href'))