You can call get() with the path to Chrome. Below is an example – replace chrome_path with the correct path for your platform.
import webbrowser
url="http://docs.python.org/"
# MacOS
chrome_path="open -a /Applications/Google\ Chrome.app %s"
# Windows
# chrome_path="C:/Program Files (x86)/Google/Chrome/Application/chrome.exe %s"
# Linux
# chrome_path="/usr/bin/google-chrome %s"
webbrowser.get(chrome_path).open(url)