Django ORM 中ForeignKey生成sql的方式

django根据model的name按照字母序升序排序， 然后依次生成sql， 例如有model A, B, C， 此时A外键引用B， C外键引用B， 则生成的sql即为：
create table app_a(...)
create table app_b(...)
create table app_c(...reference app_b(...))
alter table app_a add foreign key fkey_name reference app_b(...))

urls中pattern可以简写

from django.conf.urls.defaults import *

urlpatterns = patterns('',
(r'^$', "main.views.index"),
(r'^contact-us/$', "main.views.contact_us"),
)

可以简写为:
from django.conf.urls.defaults import *

urlpatterns = patterns('main.views',
(r'^$', "index"),
(r'^contact-us/$', "contact_us"),
)
pattern的第一个参数是一个前缀

重写django的FilterSpec来实现filter tag的数据自定义

重写django的FilterSpec来实现filter tag的数据自定义, 注意FilterSpec的register始终将新加的test function和factory的tuple放到registered list的最后, 但是当FilterSpec查找model匹配的FilterSpec的时候是顺序遍历的, 所以当在FilterSpec中只要有一个test function返回True, 那么model就用这个, 就是说model一直用第一个匹配的FilterSpec, 所以就有了下边的insert_first_filter_spec.

from django.contrib.admin.filterspecs import FilterSpec

def insert_first_filter_spec(test,factory):
FilterSpec.filter_specs.insert(0,(test,factory))

class AdvancedChoicesFilterSpec(FilterSpec):
def __init__(self, f, request, params, model):
super(AdvancedChoicesFilterSpec, self).__init__(f, request, params, model)
self.lookup_kwarg = '%s__exact' % f.name

make models's field default value to default filter
self.lookup_val = request.GET.get(self.lookup_kwarg, None) or self.field.default

def choices(self, cl):
yield {'selected': self.lookup_val is None,
'query_string': cl.get_query_string({}, [self.lookup_kwarg]),
'display': _('All')}
for k, v in self.field.choices:
yield {'selected': str(k) == self.lookup_val,
'query_string': cl.get_query_string({self.lookup_kwarg: k}),
'display': v}

replace choices tag factory
insert_first_filter_spec(lambda f: bool(f.choices), AdvancedChoicesFilterSpec)

"ago filter" / date tag filter - django snippet

from django import template
from StringIO import StringIO

register = template.Library()

@register.filter_function
def date_tag(path, tags):
"""
{{ "/recent/"|date_tag:"0,1,2,3" }}
"""
html = StringIO()
if path:
path = path.strip()
else:
path=""
tags = [x.strip() for x in tags.split(',')]
for tag in tags:
if tag == "0":
html.write('<a href="%s%s/">%s</a><br>' % (path,tag,"today"))
elif tag == "1":
html.write('<a href="%s%s/">%s</a><br>' % (path,tag,"yesterday"))
else:
html.write('<a href="%s%s/">%s</a><br>' % (path,tag,tag+" days ago"))
return html.getvalue()

===================================
usage:
1. put this code to app/templatetags directory, named tags.py
2. load tags into template: {% load tags %}
3. use filter