Note_Tech

All technological notes.

---

Project maintained by simonangel-fong Hosted on GitHub Pages — Theme by mattgraham

Django - Meta

Back

• Django - Meta
  • Meta
  • Meta options
  • _Meta
    • Attributes
    • Methods
    • Example: Get Fields Info

---

Meta

• Meta:
  • the Model metadata is “anything that’s not a field”, such as ordering options (ordering), database table name (db_table), or human-readable singular and plural names (verbose_name and verbose_name_plural).
• None are required, and adding class Meta to a model is completely optional.

---

Meta options

• Meta

Meta Opt	Description
db_table	name of the database table
verbose_name	A human-readable name for the object
verbose_name_plural	The plural name for the object
abstract	Wheter the current model is an abstract base class.
db_table_comment	comment on the database table
label	read-only, returns app_label.object_name
label_lower	read-only, returns app_label.object_name

• Contraint

Meta Opt	Description
constraints	A list of constraints
unique_together	Sets of field names that must be unique together

• index

Meta Opt	Description
indexes	A list of indexes
index_together	Sets of field names that, taken together, are indexed
db_tablespace	name of the database tablespace

• Order

Meta Opt	Description
ordering	order by
get_latest_by	name(s) of a field for latest() and earliest() methods.

---

_Meta

• _meta:
  • a class provide access to meta data of models

Attributes

from EmpApp.models import Employee

# print(type(Employee.objects))   # <class 'django.db.models.manager.Manager'>
# print(Employee.objects.all())

# Some attributes of -meta
print(Employee._meta)                       # EmpApp.employee
print(Employee._meta.app_label)             # EmpApp
print(Employee._meta.apps)
# <django.apps.registry.Apps object at 0x0000024530DD1C70>
print(Employee._meta.model)                 # <class 'EmpApp.models.Employee'>
print(Employee._meta.db_table)              # EmpApp_employee
print(Employee._meta.verbose_name)          # employee
print(Employee._meta.model_name)            # employee
print(Employee._meta.object_name)           # Employee
print(Employee._meta.constraints)           # []
print(Employee._meta.fields)
# (<django.db.models.fields.BigAutoField: id>,
# <django.db.models.fields.CharField: first_name>,
# <django.db.models.fields.CharField: last_name>,
# <django.db.models.fields.EmailField: email>)

---

Methods

Methods	Description
get_field(field_name)	Returns the field instance with a fiel name.
get_fields()	Returns a tuple of fields

from EmpApp.models import Employee

print(Employee._meta.get_field("first_name"))       # EmpApp.Employee.first_name
[print(type(f)) for f in Employee._meta.get_fields()]
# <class 'django.db.models.fields.BigAutoField'>
# <class 'django.db.models.fields.CharField'>
# <class 'django.db.models.fields.CharField'>
# <class 'django.db.models.fields.EmailField'>

---

Example: Get Fields Info

from EmpApp.models import Employee

def initiate_dict(model):
  '''initiate a dict based on a model'''
    return dict.fromkeys([f.attname for f in model._meta.get_fields()])

print(initiate_dict(Employee))  # {'id': None, 'first_name': None, 'last_name': None, 'email': None}


def datatype_conversion(dict_data, Model):
    data = dict_data

    for field in Workout._meta.fields:                  #_meta.fields返回所有字段名
        # print(field.get_internal_type())
        if field.get_internal_type() == "DecimalField":     #get_internal_type()返回字段类型，是字符串
            data[field.attname] = float(data[field.attname])
        if field.get_internal_type() == "IntegerField":
            data[field.attname] = int(data[field.attname])
    return data

---

TOP