How to check duplicate data in my datastore and display the error?

Question

Am working on GAE,GAE datastore and python.

This is my dbmodel.py,

class Customer(db.Model):
    name = db.StringProperty(required=True)
    phone = db.         


        

Answer 1

There's good Unique model available in webapp2:

For example, suppose we have a model User with three properties that must be unique across a given group: username, auth_id and email::

class User(model.Model):
    username = model.StringProperty(required=True)
    auth_id = model.StringProperty(required=True)
    email = model.StringProperty(required=True)

To ensure property uniqueness when creating a new User, we first create Unique records for those properties, and if everything goes well we can save the new User record::

@classmethod
def create_user(cls, username, auth_id, email):
    # Assemble the unique values for a given class and attribute scope.
    uniques = [
        'User.username.%s' % username,
        'User.auth_id.%s' % auth_id,
        'User.email.%s' % email,
    ]

    # Create the unique username, auth_id and email.
    success, existing = Unique.create_multi(uniques)

    if success:
        # The unique values were created, so we can save the user.
        user = User(username=username, auth_id=auth_id, email=email)
        user.put()
        return user
    else:
        # At least one of the values is not unique.
        # Make a list of the property names that failed.
        props = [name.split('.', 2)[1] for name in uniques]
        raise ValueError('Properties %r are not unique.' % props)

This is the only way to transactionally check the uniqueness.

https://webapp-improved.appspot.com/_modules/webapp2_extras/appengine/auth/models.html#Unique