Download an image from a webpage

Question

I am trying to write a Python script that download an image from a webpage. On the webpage (I am using NASA's picture of the day page), a new picture is posted everyday, with different file names. After download, set the image as desktop.

My solutions was to parse the HTML using HTMLParser, looking for "jpg", and write the path and file name of the image to an attribute (named as "output", see code below) of the HTML parser object.

The code works, but I am just looking for comments and advice. I am new to Python and OOP (this is my first real python script ever), so I am not sure if this is how it is generally done.

import urllib2
import ctypes
from HTMLParser import HTMLParser

# Grab image url
response = urllib2.urlopen('http://apod.nasa.gov/apod/astropix.html')
html = response.read()

class MyHTMLParser(HTMLParser):


    def handle_starttag(self, tag, attrs):
        # Only parse the 'anchor' tag.
        if tag == "a":
           # Check the list of defined attributes.
           for name, value in attrs:
               # If href is defined, print it.
               if name == "href":
                   if value[len(value)-3:len(value)]=="jpg":
                       #print value
                       self.output=value

parser = MyHTMLParser()
parser.feed(html)
imgurl='http://apod.nasa.gov/apod/'+parser.output
print imgurl

# Save the file
img = urllib2.urlopen(imgurl)
localFile = open('desktop.jpg', 'wb')
localFile.write(img.read())
localFile.close()

# set to desktop(windows method)
SPI_SETDESKWALLPAPER = 20 
ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER, 0, "desktop.jpg" , 0)

Answer 1

# Save the file
img = urllib2.urlopen(imgurl)
localFile = open('desktop.jpg', 'wb')
localFile.write(img.read())
localFile.close()

For opening file it's recommend to do:

with open('desktop.jpg','wb') as localFile:
     localFile.write(img.read())

Which will make sure the file closes regardless.

Also, urllib.urlretrieve does this for you.

Answer 2

Instead of value[len(value)-3:len(value)]=="jpg" you can use

value.endswith("jpg")

Answer 3

I think your class MyHTMLParser is not necessary. We can use a function instead of a class.

If you know what is Regular Expression you can using code below:

import re

def getImageLocation():
  with urllib2.urlopen('http://apod.nasa.gov/apod/astropix.html') as h:
    # (?<=...) means "Matches if the current position in the string 
    #                 is preceded by a match for ... 
    #                 that ends at the current position."
    loc = re.search('(?<=IMG SRC=")image/\d+/[\w\d_]+.jpg', a).group())
  return 'http://apod.nasa.gov/apod/' + loc

Regular Expression Syntax: http://docs.python.org/3/library/re.html#regular-expression-syntax

Answer 4

1) Have you considered searching for the img tag and just using the href from that for the desktop image?

Other than that, your code seems fine