import stripe
stripe.api_key = '26OjYWkUnwDegILl9ZNVbefRjRboRSio'
print "Attempting charge..."
resp = stripe.Charge.execute(amount=200, currency='usd', card={'number' : '4242424242424242', 'exp_month' : 10, 'exp_year' : 2014}, mnemonic='customer@gmail.com')
print 'Success: %r' % (resp, )

import stripe
stripe.api_key = '26OjYWkUnwDegILl9ZNVbefRjRboRSio'
print "Attempting charge..."
resp = stripe.Charge.execute(amount=200, currency='usd', card={'number' : '4242424242424242', 'exp_month' : 10, 'exp_year' : 2014}, description='customer@gmail.com')
print 'Success: %r' % (resp, )

Change mnemonic -> description