常见的设计模式
中文译名：设计模式 - 可复用的面向对象软件元素 中所提到的，总共有 23 种设计模式。这些模式可以分为三大类：
创建型模式（Creational Patterns）
结构型模式（Structural Patterns）
行为型模式（Behavioral Patterns）
外加，J2EE 设计模式。
创建型模式
单例模式
import threading
config_dict = {}
class Config:
def __new__(cls, *args, **kwargs):
if not hasattr(Config, "_instance"):
with threading.Lock():
if not hasattr(Config, "_instance"):
print("-----create instance-------")
Config._instance = super().__new__(cls, *args, **kwargs)
return Config._instance
def __init__(self):
self.load_config()
def load_config(self):
config_dict.update({"data_path": "ssss"})
def get_config(param):
if not config_dict:
Config()
return config_dict[param]
b = Config()
c = Config()
print(b)
print(c)
原型模式
# 当某个类，初始化操作复杂时，使用
import copy
class Book:
def __init__(self, book_name=None, author=None):
self.book_name = book_name
self.author = author
class ProtoType:
def __init__(self):
self.objects = {}
def register(self, obj_id, obj):
self.objects[obj_id] = obj
def clone(self, origin_id, **kwargs):
if not self.objects.get(origin_id):
raise Exception("Origin_id not exist!")
origin_obj = self.objects.get(origin_id)
new_obj = copy.deepcopy(origin_obj)
new_obj.__dict__.update(kwargs)
return new_obj
b_obj1 = Book(book_name="book1", author="author1")
p = ProtoType()
p.register("bbb111", b_obj1)
b_obj2 = p.clone("bbb111")
print(b_obj1 is b_obj2)
工厂模式
结构型模式
装饰器模式
from collections import defaultdict
import time
import datetime
def cal_time(limit):
def _cal_time(f):
def wrapper(*args, **kwargs):
start = time.time()
f_ret = f(*args, **kwargs)
total = time.time() - start
query = args[0].get("query")
if total > limit:
print("函数运行时间：{} 查询的query为：{}".format(total, query))
return f_ret
return wrapper
return _cal_time
def metrics(f):
def wrapper(*args, **kwargs):
f_ret = f(*args, **kwargs)
metric_dict = defaultdict(int)
for data in f_ret:
for k, v in data.items():
if k == "type":
metric_dict[v] += 1
print("metric_dict:", metric_dict)
return f_ret
return wrapper
@cal_time(0.5)
@metrics
def f(request_dict):
time.sleep(0.5)
return [{"type": "song", "value": 1}, {"type": "song", "value": 2}, {"type": "album", "value": 1}, {"type": "artist", "value": 1}]
f({"query": "a"})
MVC模式
view >> business >> handler
行为型模式
观察者模式
# 一对多关系，发布订阅模式
class Sender:
def __init__(self):
self.receivers = []
def send_msg(self, msg):
for receiver in self.receivers:
receiver.receive(msg)
def add_receiver(self, receiver):
self.receivers.append(receiver)
class Receive:
def __init__(self, receiver_id):
self.receiver_id = receiver_id
def receive(self, msg):
print("当前的接受者为：{}，接受的消息为：{}".format(self.receiver_id, msg))
s = Sender()
r1 = Receive("1")
r2 = Receive("2")
s.add_receiver(r1)
s.add_receiver(r2)
s.send_msg("第一次")
