flask之分页插件的使用、添加后保留原url搜索条件、单例模式
本篇导航：
1、django项目中写过的分页组件
from urllib.parse import urlencode,quote,unquote class Pagination(object): """ 自定义分页 """ 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 # 数据总条数 self.total_count = total_count # 每页显示10条数据 self.per_page_count = per_page_count # 页面上应该显示的最大页码 max_page_num, div = divmod(total_count, per_page_count) if div: max_page_num += 1 self.max_page_num = max_page_num # 页面上默认显示11个页码（当前页在中间） self.max_pager_count = max_pager_count self.half_max_pager_count = int((max_pager_count - 1) / 2) # URL前缀 self.base_url = base_url # request.GET import copy params = copy.deepcopy(params) # params._mutable = True get_dict = params.to_dict() # 包含当前列表页面所有的搜/索条件 # {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): # 如果总页数 <= 11 if self.max_page_num <= self.max_pager_count: pager_start = 1 pager_end = self.max_page_num # 如果总页数 > 11 else: # 如果当前页 <= 5 if self.current_page <= self.half_max_pager_count: pager_start = 1 pager_end = self.max_pager_count else: # 当前页 + 5 > 总页码 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 #倒这数11个 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]} # 首页 self.params['page'] = 1 first_page = '<li><a href="%s?%s">首页</a></li>' % (self.base_url,urlencode(self.params),) page_html_list.append(first_page) # 上一页 self.params["page"] = self.current_page - 1 if self.params["page"] < 1: pervious_page = '<li class="disabled"><a href="%s?%s" aria-label="Previous">上一页</span></a></li>' % (self.base_url, urlencode(self.params)) else: pervious_page = '<li><a href = "%s?%s" aria-label = "Previous" >上一页</span></a></li>' % ( self.base_url, urlencode(self.params)) page_html_list.append(pervious_page) # 中间页码 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) # 下一页 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">下一页</span></a></li >' % (self.base_url, urlencode(self.params)) else: next_page = '<li><a href = "%s?%s" aria-label = "Next">下一页</span></a></li>' % (self.base_url, urlencode(self.params)) page_html_list.append(next_page) # 尾页 self.params['page'] = self.max_page_num last_page = '<li><a href="%s?%s">尾页</a></li>' % (self.base_url, urlencode(self.params),) page_html_list.append(last_page) return ''.join(page_html_list)
2、组件的使用
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() # ===============保留当前的跳转路径的条件============= get_dict = request.args.to_dict() # {'page': '2', 'name': '9'} path = urlencode(get_dict) # 转化成urlencode格式的 get_dict["_list_filter"] = path path = urlencode(get_dict) # 转化成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>
单例模式是设计模式中最简单的形式之一。这一模式的目的是使得类的一个对象成为系统中的唯一实例。要实现这一点，可以从客户端对其进行实例化开始。因此需要用一种只允许生成对象类的唯一实例的机制，下面有四种实现方式
1、文件导入的形式
s1.py class Foo(object): def test(self): print("123") v = Foo() #v是Foo的实例 s2.py 复制代码 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 # 两个的内存地址是一样的 # 文件加载的时候，第一次导入后，再次导入时不会再重新加载。
2、基于类实现的单例模式
# ======================单例模式：无法支持多线程情况=============== 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() # ====================单例模式：支持多线程情况================、 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: #为了保证线程安全在内部加锁 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) # 使用先说明，以后用单例模式，obj = Singleton.instance() # 示例： # obj1 = Singleton.instance() # obj2 = Singleton.instance() # print(obj1,obj2) # 错误示例 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2)
3、基于__new__实现的单例模式（最常用）
# =============单线程下执行=============== 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"): # 类加括号就回去执行__new__方法，__new__方法会创建一个类实例：Singleton() Singleton._instance = object.__new__(cls, *args, **kwargs) # 继承object类的__new__方法，类去调用方法，说明是函数，要手动传cls return Singleton._instance #obj1 #类加括号就会先去执行__new__方法，在执行__init__方法 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2) # ===========多线程执行单利============ def task(arg): obj = Singleton() print(obj) for i in range(10): t = threading.Thread(target=task,args=[i,]) t.start() # 使用先说明，以后用单例模式，obj = Singleton() # 示例 # obj1 = Singleton() # obj2 = Singleton() # print(obj1,obj2)
4、基于mateclass实现的单例模式
""" 1.对象是类创建，创建对象时候类的__init__方法自动执行，对象()执行类的 __call__ 方法 2.类是type创建，创建类时候type的__init__方法自动执行，类() 执行type的 __call__方法(类的__new__方法,类的__init__方法) # 第0步: 执行type的 __init__ 方法【类是type的对象】 class Foo: def __init__(self): pass def __call__(self, *args, **kwargs): pass # 第1步: 执行type的 __call__ 方法 # 1.1 调用 Foo类（是type的对象）的 __new__方法，用于创建对象。 # 1.2 调用 Foo类（是type的对象）的 __init__方法，用于对对象初始化。 obj = Foo() # 第2步：执行Foo的 __call__ 方法 obj() """ # ===========类的执行流程================ class SingletonType(type): def __init__(self,*args,**kwargs): print(self) #会不会打印？ #<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、对象是类创建的，创建对象时类的__init__方法会自动执行，对象（）执行类的__call__方法 2、类是type创建的，创建类时候type类的__init__方法会自动执行，类（）会先执行type的__call__方法（调用类的__new__，__init__方法） Foo 这个类是由SingletonType这个类创建的 ''' obj = Foo("hiayan") # ============第三种方式实现单例模式================= 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)
