Django

源码中各种有用的中间件

数据库中的zlib

http://stackoverflow.com/questions/875122/zlib-in-database-django

from base64 import binascii

f = VCFile(head = binascii.b2a_base64('blahblah'.encode('zlib')))

ORM

http://www.eflorenzano.com/blog/post/secrets-django-orm/

[[>>>]] qs = TumbleItem.objects.all()
>>> qs.query.group_by = ['item_type']
>>> qs.query.having = ['COUNT(item_type) > 1']
>>> item_types = [i.item_type for i in qs]
>>> item_types
[u'blog', u'digg']

大数

新版Django已经支持

http://www.numlock.ch/news/it/django-custom-model-field-for-an-unsigned-bigint-data-type/

from django.db import models
from django.db.models.fields import PositiveIntegerField

class PositiveBigIntegerField(PositiveIntegerField):
    """Represents MySQL's unsigned BIGINT data type (works with MySQL only!)"""
    empty_strings_allowed = False

    def get_internal_type(self):
        return "PositiveBigIntegerField"

    def db_type(self):
        # This is how MySQL defines 64 bit unsigned integer data types
        return "bigint UNSIGNED"

class Mytest(models.Model):
    """Just a test model"""

    huge_id = PositiveBigIntegerField()

    def __unicode__(self):
        return u'id: %s, huge_id: %s' % (self.id, self.huge_id)

序列化

python ui/manage.py loaddata site.json

from django.core import serializers

from django.core.management import setup_environ
from myproject.ui import settings
setup_environ(settings)
from myproject.ui.models import Task

task = Task.objects.get(id=9527)
all_objects = [task]

json_serializer = serializers.get_serializer('json')()
json_serializer.serialize(all_objects, ensure_ascii=True, stream=open('site.json', 'w'))

乘除法

http://my.oschina.net/renwofei423/blog/12713

django 模板的乘法，除法

Note: The results are rounded to an integer before returning, so this may have marginal utility for many cases.

So, in summary:

to compute A*B: {% widthratio A 1 B %}
to compute A/B: {% widthratio AB 1 %}

And, since add is a filter and not a tag, you can always to crazy stuff like:

compute A^2: {% widthratio A 1 A %}
compute (A+B)^2: {% widthratio A|add:B 1 A|add:B %}
compute (A+B) * (C+D): {% widthratio A|add:B 1 C|add:D %}

原文出处：http://slacy.com/blog/2010/07/using-djangos-widthratio-template-tag-for-multiplication-division/