def isCommaSeparatedEmailList(field_data, all_data):
    for supposed_email in field_data.split(','):
        try:
            isValidEmail(supposed_email.strip(), '')
        except ValidationError:
            raise ValidationError, gettext("Enter valid e-mail addresses separated by commas.")
Checks that field_data is a string of e-mail addresses separated by commas.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-0.96/django/core/validators.py/isCommaSeparatedEmailList