def login():
'''
Used for login and logging out (if no username is passed)
'''
dbnumber=app.config['db']
username = request.form.get('username', None)
if request.method == 'POST':
u = User(dbnumber, username = username)
if u.isvalid and u.checkpassword(request.form['password']):
session['loggedin'] = u.username
else:
session['loggedin'] = None
return redirect(url_for('root'))
