Django Sequence Field

A Django field for creating templated sequenced strings.

Usage:

Importing and using the SequenceField class:

from sequence_field.fields import SequenceField

# Create your models here.

class TestModel(models.Model):

    sequence = SequenceField(
        key='test.sequence.1',
        template='%Y%m%d${code}%NNNNN',
        params={'code':'ABC'},
        auto=True
    )
 

When creating new objects, the sequence is generated automatically based on the template:

from my_app.models import TestModel

obj = TestModel()
obj.save()

print(obj.sequence) # 20140703ABC00001

obj = TestModel()
obj.save()

print(obj.sequence) # 20140703ABC00002

An accompaning Sequence model is used by this app to store the current value for each key. When a new key is declared in a field a new Sequence instance is created and saved on the fly.

If you need to customize the creation of each sequence value passing different parameters you'll have to do it at the model level with code like this:

from sequence_field.models import Sequence
print(Sequence.next('test.sequence.1', template='%Y%m%d${code}%NNNNN', params={'code':'XYZ'})) # 20140703XYZ00003

Templates can also be stored in the database so you don't have to pass them all the time. If a template is provided the first time a key is used it gets automatically stored.

>>> from sequence_field.models import Sequence
>>> Sequence.next('test.sequence.20', template='%m%d%Y-%NNNNNNNNNNN')
'07042014-00000000001'
>>> Sequence.next('test.sequence.20')
'07042014-00000000002'

You can use the provided Expander classes or build your own. As an example see the code for the TimeExpander class the uses Python's strftime function to perform time-related expansions:

class TimeExpander(BaseExpander):                                               
                                                                                
    def expand(self, template=None, count=None, params={}, value=None):         
        import time                                                             
        (template, count, params, value) = self.setvars(                        
            template, count, params, value                                      
        )                                                                       
        return time.strftime(value)

The default expanders are: (taken from the constants.py file)

SEQUENCE_FIELD_DEFAULT_EXPANDERS = (                                            
    'sequence_field.expanders.NumericExpander',                                 
    'sequence_field.expanders.TimeExpander',                                    
    'sequence_field.expanders.ParameterExpander',                               
) 

At your Django project's settings.py file you can customize this variables: (default values are shown)

SEQUENCE_FIELD_DEFAULT_VALUE # 1

SEQUENCE_FIELD_ADMIN # True

SEQUENCE_FIELD_DEFAULT_TEMPLATE # '%N'

SEQUENCE_FIELD_DEFAULT_PATTERN #  r'(\d+)'

SEQUENCE_FIELD_DEFAULT_EXPANDERS # Already mentioned in the previous section.

Installation from Github

pip install https://github.com/marquicus/django-sequence-field/zipball/master

Add this line to your requirements.txt file:

-e git+https://github.com/marquicus/django-sequence-field.git@HEAD#egg=django-sequence-field

Then just run:

pip install -r requirements.txt.

(c) 2014 Antonio Ognio antonio@ognio.com