import re
import mechanize

br = mechanize.Browser()
br.open("http://example.com")

username = "1******a"
password = "Hu*********3"
site = br.open("http://example.com")
br.select_form(nr=1)
br.form['session[Client_username]'] = username
br.form['session[Client_login_mode]'] = password
br.submit()