Changing user agent on urllib2.urlopen

Question

I answered a similar question a couple weeks ago.

There is example code in that question, but basically you can do something like this: (Note the capitalization of User-Agent as of RFC 2616, section 14.43.)

opener = urllib2.build_opener()
opener.addheaders = [('User-Agent', 'Mozilla/5.0')]
response = opener.open('http://www.stackoverflow.com')

headers = { 'User-Agent' : 'Mozilla/5.0' }
req = urllib2.Request('www.example.com', None, headers)
html = urllib2.urlopen(req).read()

Or, a bit shorter:

req = urllib2.Request('www.example.com', headers={ 'User-Agent': 'Mozilla/5.0' })
html = urllib2.urlopen(req).read()

Setting the User-Agent from everyone's favorite Dive Into Python.

The short story: You can use Request.add_header to do this.

You can also pass the headers as a dictionary when creating the Request itself, as the docs note:

headers should be a dictionary, and will be treated as if add_header() was called with each key and value as arguments. This is often used to “spoof” the User-Agent header, which is used by a browser to identify itself – some HTTP servers only allow requests coming from common browsers as opposed to scripts. For example, Mozilla Firefox may identify itself as "Mozilla/5.0 (X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11", while urllib2‘s default user agent string is "Python-urllib/2.6" (on Python 2.6).

For python 3, urllib is split into 3 modules...

import urllib.request
req = urllib.request.Request(url="http://localhost/", headers={'User-Agent':' Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20100101 Firefox/12.0'})
handler = urllib.request.urlopen(req)

All these should work in theory, but (with Python 2.7.2 on Windows at least) any time you send a custom User-agent header, urllib2 doesn't send that header. If you don't try to send a User-agent header, it sends the default Python / urllib2

None of these methods seem to work for adding User-agent but they work for other headers:

opener = urllib2.build_opener(proxy)
opener.addheaders = {'User-agent':'Custom user agent'}
urllib2.install_opener(opener)

request = urllib2.Request(url, headers={'User-agent':'Custom user agent'})

request.headers['User-agent'] = 'Custom user agent'

request.add_header('User-agent', 'Custom user agent')

For urllib you can use:

from urllib import FancyURLopener

class MyOpener(FancyURLopener, object):
    version = 'Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.8.1.11) Gecko/20071127 Firefox/2.0.0.11'

myopener = MyOpener()
myopener.retrieve('https://www.google.com/search?q=test', 'useragent.html')

Another solution in urllib2 and Python 2.7:

req = urllib2.Request('http://www.example.com/')
req.add_unredirected_header('User-Agent', 'Custom User-Agent')
urllib2.urlopen(req)