本篇導航：
1、django項目中寫過的分頁組件
from urllib.parse import urlencode,quote,unquote class Pagination(object): """ 自定義分頁 """ def __init__(self,current_page,total_count,base_url,params,per_page_count=10,max_pager_count=11): try: current_page = int(current_page) except Exception as e: current_page = 1 if current_page <=0: current_page = 1 self.current_page = current_page # 數據總條數 self.total_count = total_count # 每頁顯示10條數據 self.per_page_count = per_page_count # 頁面上應該顯示的最大頁碼 max_page_num, div = divmod(total_count, per_page_count) if div: max_page_num += 1 self.max_page_num = max_page_num # 頁面上默認顯示11個頁碼（當前頁在中間） self.max_pager_count = max_pager_count self.half_max_pager_count = int((max_pager_count - 1) / 2) # URL前綴 self.base_url = base_url # request.GET import copy params = copy.deepcopy(params) # params._mutable = True get_dict = params.to_dict() # 包含當前列表頁面所有的搜/索條件 # {source:[2,], status:[2], gender:[2],consultant:[1],page:[1]} # self.params[page] = 8 # self.params.urlencode() # source=2&status=2&gender=2&consultant=1&page=8 # href="/hosts/?source=2&status=2&gender=2&consultant=1&page=8" # href="%s?%s" %(self.base_url,self.params.urlencode()) self.params = get_dict @property def start(self): return (self.current_page - 1) * self.per_page_count @property def end(self): return self.current_page * self.per_page_count def page_html(self): # 如果總頁數 <= 11 if self.max_page_num <= self.max_pager_count: pager_start = 1 pager_end = self.max_page_num # 如果總頁數 > 11 else: # 如果當前頁 <= 5 if self.current_page <= self.half_max_pager_count: pager_start = 1 pager_end = self.max_pager_count else: # 當前頁 + 5 > 總頁碼 if (self.current_page + self.half_max_pager_count) > self.max_page_num: pager_end = self.max_page_num pager_start = self.max_page_num - self.max_pager_count + 1 #倒這數11個 else: pager_start = self.current_page - self.half_max_pager_count pager_end = self.current_page + self.half_max_pager_count page_html_list = [] # {source:[2,], status:[2], gender:[2],consultant:[1],page:[1]} # 首頁 self.params['page'] = 1 first_page = '<li><a href="%s?%s">首頁</a></li>' % (self.base_url,urlencode(self.params),) page_html_list.append(first_page) # 上一頁 self.params["page"] = self.current_page - 1 if self.params["page"] < 1: pervious_page = '<li class="disabled"><a href="%s?%s" aria-label="Previous">上一頁</span></a></li>' % (self.base_url, urlencode(self.params)) else: pervious_page = '<li><a href = "%s?%s" aria-label = "Previous" >上一頁</span></a></li>' % ( self.base_url, urlencode(self.params)) page_html_list.append(pervious_page) # 中間頁碼 for i in range(pager_start, pager_end + 1): self.params['page'] = i if i == self.current_page: temp = '<li class="active"><a href="%s?%s">%s</a></li>' % (self.base_url,urlencode(self.params), i,) else: temp = '<li><a href="%s?%s">%s</a></li>' % (self.base_url,urlencode(self.params), i,) page_html_list.append(temp) # 下一頁 self.params["page"] = self.current_page + 1 if self.params["page"] > self.max_page_num: self.params["page"] = self.current_page next_page = '<li class="disabled"><a href = "%s?%s" aria-label = "Next">下一頁</span></a></li >' % (self.base_url, urlencode(self.params)) else: next_page = '<li><a href = "%s?%s" aria-label = "Next">下一頁</span></a></li>' % (self.base_url, urlencode(self.params)) page_html_list.append(next_page) # 尾頁 self.params['page'] = self.max_page_num last_page = '<li><a href="%s?%s">尾頁</a></li>' % (self.base_url, urlencode(self.params),) page_html_list.append(last_page) return ''.join(page_html_list)
2、組件的使用
from flask import Flask,render_template,request,redirect from pager import Pagination from urllib.parse import urlencode app = Flask(__name__) =========================django的用法======================================= # pager_obj = Pagination(request.GET.get('page', 1), len(HOST_LIST), request.path_info, request.GET) # host_list = HOST_LIST[pager_obj.start:pager_obj.end] # html = pager_obj.page_html() # return render(request, 'hosts.html', {'host_list': host_list, "page_html": html}) @app.route('/pager') def pager(): li = [] for i in range(1,100): li.append(i) # print(li) ===================================flask的用法=============================== pager_obj = Pagination(request.args.get("page",1),len(li),request.path,request.args,per_page_count=10) # print(request.args) index_list = li[pager_obj.start:pager_obj.end] html = pager_obj.page_html() return render_template("pager.html",index_list=index_list, html = html,condition=path) if __name__ == '__main__': app.run(debug=True)
3、pager.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width"> <title>Title</title> <link rel="stylesheet" href="/static/bootstrap-3.3.7-dist/css/bootstrap.min.css"> <style> .container{ margin-top: 20px; } </style> </head> <body> <div class="container"> <a href="/add?{{ condition }}"><button class="btn btn-primary">添加</button></a> <div class="row " style="margin-top: 10px"> <ul> {% for foo in index_list %} <li>{{ foo }}</li> {% endfor %} </ul> <nav aria-label="Page navigation" class="pull-right"> <ul class="pagination"> {{ html|safe }} </ul> </nav> </div> </div> </body> </html>
1、run.py
#!usr/bin/env python # -*- coding:utf-8 -*- from flask import Flask,render_template,request,redirect from pager import Pagination from urllib.parse import urlencode app = Flask(__name__) @app.route('/pager') def pager(): li = [] for i in range(1,100): li.append(i) # print(li) pager_obj = Pagination(request.args.get("page",1),len(li),request.path,request.args,per_page_count=10) # print(request.args) index_list = li[pager_obj.start:pager_obj.end] html = pager_obj.page_html() # ===============保留當前的跳轉路徑的條件============= get_dict = request.args.to_dict() # {'page': '2', 'name': '9'} path = urlencode(get_dict) # 轉化成urlencode格式的 get_dict["_list_filter"] = path path = urlencode(get_dict) # 轉化成urlencode格式的 print(path) # page=5&aaa=1&_list_filter=page%3D5%26aaa%3D1 print(get_dict) # {'page': '10', '_list_filter': 'page=10'} return render_template("pager.html",index_list=index_list, html = html,condition=path) @app.route('/add',methods=["GET","POST"]) def add(): if request.method =="GET": return render_template("add.html") else: url = request.args.get("_list_filter") # print(url) return redirect("/pager?%s"%url) if __name__ == '__main__': app.run(debug=True)
2、pager.html
<a href="/add?{{ condition }}"><button class="btn btn-primary">添加</button></a>
3、add.html
<form action="" method="post"> <input type="text"> <input type="submit" value="提交"> </form>
單例模式是設計模式中最簡單的形式之一。這一模式的目的是使得類的一個對象成為系統中的唯一實例。要實現這一點，可以從客戶端對其進行實例化開始。因此需要用一種只允許生成對象類的唯一實例的機制，下面有四種實現方式
1、文件導入的形式
s1.py class Foo(object): def test(self): print("123") v = Foo() #v是Foo的實例 s2.py 復制代碼 from s1 import v as v1 print(v1,id(v1)) #<s1.Foo object at 0x0000000002221710> 35788560 from s1 import v as v2 print(v1,id(v2)) #<s1.Foo object at 0x0000000002221710> 35788560 # 兩個的內存地址是一樣的 # 文件加載的時候，第一次導入后，再次導入時不會再重新加載。
2、基於類實現的單例模式
# ======================單例模式：無法支持多線程情況=============== class Singleton(object): def __init__(self): import time time.sleep(1) @classmethod def instance(cls, *args, **kwargs): if not hasattr(Singleton, "_instance"): Singleton._instance = Singleton(*args, **kwargs) return Singleton._instance import threading def task(arg): obj = Singleton.instance() print(obj) for i in range(10): t = threading.Thread(target=task,args=[i,]) t.start() # ====================單例模式：支持多線程情況================、 import time import threading class Singleton(object): _instance_lock = threading.Lock() def __init__(self): time.sleep(1) @classmethod def instance(cls, *args, **kwargs): if not hasattr(Singleton, "_instance"): with Singleton._instance_lock: #為了保證線程安全在內部加鎖 if not hasattr(Singleton, "_instance"): Singleton._instance = Singleton(*args, **kwargs) return Singleton._instance def task(arg): obj = Singleton.instance() print(obj) for i in range(10): t = threading.Thread(target=task,args=[i,]) t.start() time.sleep(20) obj = Singleton.instance() print(obj) # 使用先說明，以后用單例模式，obj = Singleton.instance() # 示例： # obj1 = Singleton.instance() # obj2 = Singleton.instance() # print(obj1,obj2) # 錯誤示例 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2)
3、基於__new__實現的單例模式（最常用）
# =============單線程下執行=============== import threading class Singleton(object): _instance_lock = threading.Lock() def __init__(self): pass def __new__(cls, *args, **kwargs): if not hasattr(Singleton, "_instance"): with Singleton._instance_lock: if not hasattr(Singleton, "_instance"): # 類加括號就回去執行__new__方法，__new__方法會創建一個類實例：Singleton() Singleton._instance = object.__new__(cls, *args, **kwargs) # 繼承object類的__new__方法，類去調用方法，說明是函數，要手動傳cls return Singleton._instance #obj1 #類加括號就會先去執行__new__方法，在執行__init__方法 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2) # ===========多線程執行單利============ def task(arg): obj = Singleton() print(obj) for i in range(10): t = threading.Thread(target=task,args=[i,]) t.start() # 使用先說明，以后用單例模式，obj = Singleton() # 示例 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2)
4、基於mateclass實現的單例模式
""" 1.對象是類創建，創建對象時候類的__init__方法自動執行，對象()執行類的 __call__ 方法 2.類是type創建，創建類時候type的__init__方法自動執行，類() 執行type的 __call__方法(類的__new__方法,類的__init__方法) # 第0步: 執行type的 __init__ 方法【類是type的對象】 class Foo: def __init__(self): pass def __call__(self, *args, **kwargs): pass # 第1步: 執行type的 __call__ 方法 # 1.1 調用 Foo類（是type的對象）的 __new__方法，用於創建對象。 # 1.2 調用 Foo類（是type的對象）的 __init__方法，用於對對象初始化。 obj = Foo() # 第2步：執行Foo的 __call__ 方法 obj() """ # ===========類的執行流程================ class SingletonType(type): def __init__(self,*args,**kwargs): print(self) #會不會打印？ #<class '__main__.Foo'> super(SingletonType,self).__init__(*args,**kwargs) def __call__(cls, *args, **kwargs): #cls = Foo obj = cls.__new__(cls, *args, **kwargs) obj.__init__(*args, **kwargs) return obj class Foo(metaclass=SingletonType): def __init__(self,name): self.name = name def __new__(cls, *args, **kwargs): return object.__new__(cls, *args, **kwargs) ''' 1、對象是類創建的，創建對象時類的__init__方法會自動執行，對象（）執行類的__call__方法 2、類是type創建的，創建類時候type類的__init__方法會自動執行，類（）會先執行type的__call__方法（調用類的__new__，__init__方法） Foo 這個類是由SingletonType這個類創建的 ''' obj = Foo("hiayan") # ============第三種方式實現單例模式================= import threading class SingletonType(type): _instance_lock = threading.Lock() def __call__(cls, *args, **kwargs): if not hasattr(cls, "_instance"): with SingletonType._instance_lock: if not hasattr(cls, "_instance"): cls._instance = super(SingletonType,cls).__call__(*args, **kwargs) return cls._instance class Foo(metaclass=SingletonType): def __init__(self,name): self.name = name obj1 = Foo('name') obj2 = Foo('name') print(obj1,obj2)