Python download image with lxml

I need to find an image in a HTML code similar to this one: ``` ... <a href="/example/1"> <img id="img" src="http://example.net/example.jpg" alt="Example" /> </a> ... ``` I am using lxml and requests. Here is the code: ``` import lxml from lxml import html import requests url = 'http://www.example.com' r = requests.get(url) tree = lxml.html.fromstring(r.content) img = tree.get_element_by_id("img") f = open("image.jpg",'wb') f.write(requests.get(img['src']).content) ``` But i am getting an error: ``` Traceback (most recent call last): File "/Users/Name/Documents/Python/Example/Script.py", line 13, in <module> s = requests.get(img['src']) File "/Library/Python/2.6/site-packages/lxml/lxml.etree.pyx", line 1052, in lxml.etree._Element.__getitem__ (src/lxml/lxml.etree.c:38272) TypeError: 'str' object cannot be interpreted as an index ``` Suggestions?