這篇文章帶給大家的內容是關於Django admin原始碼的分析（附範例），有一定的參考價值，有需要的朋友可以參考一下，希望對你有幫助。
單例模式（Singleton Pattern）是一種常用的軟體設計模式，該模式的主要目的是確保某一個類別只有一個實例存在。當你希望在整個系統中，某個類別只能出現一個實例時，單例物件就能派上用場。
例如，某個伺服器程式的設定資訊存放在一個檔案中，客戶端透過一個 AppConfig 的類別來讀取設定檔的資訊。如果在程式運行期間，有很多地方都需要使用設定檔的內容，也就是說很多地方都需要創建AppConfig 對象的實例，這就導致系統中存在多個AppConfig 的實例對象，而這樣會嚴重浪費記憶體資源，尤其是在設定檔內容很多的情況下。事實上，類似 AppConfig 這樣的類，我們希望在程式運行期間只存在一個實例物件。
在Python 中，我們可以用多種方法來實作單例模式：
#使用__new__()
__new__()
來控制實例的建立過程，程式碼如下：__new__()方法用來建立實例物件__init__()方法用來初始化實例物件
class Person(object):
def __init__(self, name, age):
self.name = name
self.age = age
class Singleton(object):
_instance = None
def __new__(cls, *args, **kwargs):
print(1)
if not cls._instance:
cls._instance = super(Singleton, cls).__new__(cls)
return cls._instance
def __init__(self, name, age):
print(2)
self.name = name
self.age = age
if __name__ == '__main__':
p1 = Person("djb", 18)
p2 = Person("djb", 18)
print(p1 == p2)
print(id(p1), id(p2))
print("=" * 120)
s1 = Singleton("djb", 18)
s2 = Singleton("djb", 18)
print(s1 == s2)
print(id(s1), id(s2))class Singleton(object):
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Singleton("djb", 18)from singleton import p1 print(id(p1)) print(p1.name) p1.name = "Bob" from singleton import p1 print(id(p1)) print(p1.name)
def autodiscover():
autodiscover_modules('admin', register_to=site)＃admin.py
class BookAdmin(admin.ModelAdmin):
list_display = ("title",'publishDate', 'price')
admin.site.register(Book, BookAdmin)
admin.site.register(Publish)admin.site.register(Book, BookAdmin) admin.site.register(Publish)
class ModelAdmin(BaseModelAdmin):pass
def register(self, model_or_iterable, admin_class=None, **options):
if not admin_class:
admin_class = ModelAdmin
# Instantiate the admin class to save in the registry
self._registry[model] = admin_class(model, self)urlpatterns = [
url(r'^admin/', admin.site.urls),
]class AdminSite(object):
def get_urls(self):
from django.conf.urls import url, include
urlpatterns = []
# Add in each model's views, and create a list of valid URLS for the
# app_index
valid_app_labels = []
for model, model_admin in self._registry.items():
urlpatterns += [
url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(model_admin.urls)),
]
if model._meta.app_label not in valid_app_labels:
valid_app_labels.append(model._meta.app_label)
return urlpatterns
@property
def urls(self):
return self.get_urls(), 'admin', self.namefrom django.shortcuts import HttpResponse
def test01(request):
return HttpResponse("test01")
def test02(request):
return HttpResponse("test02")
urlpatterns = [
url(r'^admin/', admin.site.urls),
url(r'^Xadmin/', ([
url(r'^test01/', test01),
url(r'^test02/', test02),
],None,None)),
]from django.conf.urls import url,include
from django.contrib import admin
from django.shortcuts import HttpResponse
def change_list_view(request):
return HttpResponse("change_list_view")
def add_view(request):
return HttpResponse("add_view")
def delete_view(request):
return HttpResponse("delete_view")
def change_view(request):
return HttpResponse("change_view")
def get_urls():
temp=[
url(r"^$".format(app_name,model_name),change_list_view),
url(r"^add/$".format(app_name,model_name),add_view),
url(r"^\d+/del/$".format(app_name,model_name),delete_view),
url(r"^\d+/change/$".format(app_name,model_name),change_view),
]
return temp
url_list=[]
for model_class,obj in admin.site._registry.items():
model_name=model_class._meta.model_name
app_name=model_class._meta.app_label
# temp=url(r"{0}/{1}/".format(app_name,model_name),(get_urls(),None,None))
temp=url(r"{0}/{1}/".format(app_name,model_name),include(get_urls()))
url_list.append(temp)
urlpatterns = [
url(r'^admin/', admin.site.urls),
url(r'^Xadmin/', (url_list,None,None)),
]以上是Django admin原始碼的分析（附範例）的詳細內容。更多資訊請關注PHP中文網其他相關文章！
