class Variance(expression, sample=False, **extra) [source] Returns the variance of the data in the provided expression. Default alias: <field>__variance Return type: float Has one optional argument: sample By default, Variance returns the population variance. However, if sample=True, the return value will be the sample variance. SQLite SQLite doesn’t provide Variance out of the box. An implementation is available as an extension module for SQLite. Consult the SQlite document

class Value(value, output_field=None) [source] A Value() object represents the smallest possible component of an expression: a simple value. When you need to represent the value of an integer, boolean, or string within an expression, you can wrap that value within a Value(). You will rarely need to use Value() directly. When you write the expression F('field') + 1, Django implicitly wraps the 1 in a Value(), allowing simple values to be used in more complex expressions. You will need to use

class UUIDField(**options) [source] A field for storing universally unique identifiers. Uses Python’s UUID class. When used on PostgreSQL, this stores in a uuid datatype, otherwise in a char(32). Universally unique identifiers are a good alternative to AutoField for primary_key. The database will not generate the UUID for you, so it is recommended to use default: import uuid from django.db import models class MyUUIDModel(models.Model): id = models.UUIDField(primary_key=True, default=uui

class URLField(max_length=200, **options) [source] A CharField for a URL. The default form widget for this field is a TextInput. Like all CharField subclasses, URLField takes the optional max_length argument. If you don’t specify max_length, a default of 200 is used.

output_field Defines the class this transformation outputs. It must be a Field instance. By default is the same as its lhs.output_field.

lookup_name The name of the lookup, used for identifying it on parsing query expressions. It cannot contain the string "__".

lhs The left-hand side - what is being transformed. It must follow the Query Expression API.

bilateral A boolean indicating whether this transformation should apply to both lhs and rhs. Bilateral transformations will be applied to rhs in the same order as they appear in the lookup expression. By default it is set to False. For example usage, see Custom Lookups.

class Transform [source] A Transform is a generic class to implement field transformations. A prominent example is __year that transforms a DateField into a IntegerField. The notation to use a Transform in an lookup expression is <expression>__<transformation> (e.g. date__year). This class follows the Query Expression API, which implies that you can use <expression>__<transform1>__<transform2>. It’s a specialized Func() expression that only accepts one argument.

class TimeField(auto_now=False, auto_now_add=False, **options) [source] A time, represented in Python by a datetime.time instance. Accepts the same auto-population options as DateField. The default form widget for this field is a TextInput. The admin adds some JavaScript shortcuts.