djandgo model id

django 关于model id：

Automatic primary key fields
By default, Django gives each model the following field:

id = models.AutoField(primary_key=True)
This is an auto-incrementing primary key.

If you’d like to specify a custom primary key, just specify primary_key=True on one of your fields. If Django sees you’ve explicitly set Field.primary_key, it won’t add the automatic id column.

Each model requires exactly one field to have primary_key=True.

　　来源：http://django-chinese-docs.readthedocs.org/en/latest/topics/db/models.html#automatic-primary-key-fields