Learning Python

Internet-Related Activities

The Internet is a treasure trove of information, but its exponential growth can make it hard to manage. Furthermore, most tools currently available for “surfing the Web” are not programmable. Many web-related tasks can be automated quite simply with the tools in the standard Python distribution.

Downloading a Web Page Programmatically

If you’re interested in finding out what the weather in a given location is over a period of months, it’s much easier to set up an automated program to get the information and collect it in a file than to have to remember to do it by hand.

Here is a program that finds the weather in a couple of cities and states using the pages of the weather.com web site:

import urllib, urlparse, string, time

def get_temperature(country, state, city):
    url = urlparse.urljoin('http://www.weather.com/weather/cities/',
                           string.lower(country)+'_' + \
                           string.lower(state) + '_' + \
                           string.replace(string.lower(city), ' ',
                                          '_') + '.html')
    data = urllib.urlopen(url).read()
    start = string.index(data, 'current temp: ') + len('current temp: ')
    stop = string.index(data, '°F', start-1)
    temp = int(data[start:stop])
    localtime = time.asctime(time.localtime(time.time()))
    print ("On %(localtime)s, the temperature in %(city)s, " +\
           "%(state)s %(country)s is %(temp)s F.") % vars()

get_temperature('FR', '', 'Paris')
get_temperature('US', 'RI', 'Providence')
get_temperature('US', 'CA', 'San Francisco')

When run, it produces output like:

~/book:> python get_temperature.py ...