Commit fec342df by Őry Máté

common: add HumanSortField

parent bedb2e12
from collections import deque
from hashlib import sha224
from logging import getLogger
from time import time
......@@ -139,3 +140,78 @@ def method_cache(memcached_seconds=60, instance_seconds=5): # noqa
return x
return inner_cache
class HumanSortField(CharField):
A CharField that monitors another field on the same model and sets itself
to a normalized value, which can be used for sensible lexicographycal
sorting for fields containing numerals. (Avoiding technically correct
orderings like [a1, a10, a2], which can be annoying for file or host
Apart from CharField's default arguments, an argument is requered:
- monitor sets the base field, whose value is normalized.
- maximum_number_length can also be provided, and defaults to 4. If
you have to sort values containing numbers greater than 9999, you
should increase it.
Code is based on carljm's django-model-utils.
def __init__(self, *args, **kwargs):
logger.debug('Initing HumanSortField(%s %s)',
unicode(args), unicode(kwargs))
kwargs.setdefault('default', "")
self.maximum_number_length = kwargs.pop('maximum_number_length', 4)
monitor = kwargs.pop('monitor', None)
if not monitor:
raise TypeError(
'%s requires a "monitor" argument' % self.__class__.__name__)
self.monitor = monitor
kwargs['blank'] = True
super(HumanSortField, self).__init__(*args, **kwargs)
def get_monitored_value(self, instance):
return getattr(instance, self.monitor)
def get_normalized_value(self, val):
def partition(s, pred):
match, notmatch = deque(), deque()
while s and pred(s[0]):
while s and not pred(s[0]):
return (''.join(match), ''.join(notmatch), s)
logger.debug('Normalizing value: %s', val)
norm = ""
val = deque(val)
while val:
numbers, letters, val = partition(val, lambda s: s[0].isdigit())
norm += numbers and numbers.rjust(self.maximum_number_length, '0')
norm += letters
logger.debug('Normalized value: %s', norm)
return norm
def pre_save(self, model_instance, add):
logger.debug('Pre-saving %s.%s. %s',
model_instance, self.attname, add)
value = self.get_normalized_value(
setattr(model_instance, self.attname, value[:self.max_length])
return super(HumanSortField, self).pre_save(model_instance, add)
# allow South to handle these fields smoothly
from south.modelsinspector import add_introspection_rules
{'monitor': ('monitor', {}),
'maximum_number_length': ('maximum_number_length', {}), }
], patterns=['common\.models\.'])
except ImportError:
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