Python内置方法和属性应用：反射和单例(推荐)

list1 = [1, 2, 3, 4] 
 list2 = [4, 3, 2, 1] 
 for idx, value in enumerate(list1): 
 print(idx, value, list2[idx]) 
 # 0 1 4 
 # 1 2 3 
 # 2 3 2 
 # 3 4 1 

# 给list加上序号 
 b = [4, 3, 2, 1] 
 for i in zip(range(len(b)), b): 
 print(i) 
 # (0, 4) 
 # (1, 3) 
 # (2, 2) 
 # (3, 1) 

@staticmethod 
 def test(): 
 print('this is static method') 
 Foo.test = test 
 Foo.test() 

class Foo(): 
 """this is test class""" 
 def __init__(self, name): 
 self.name = name 
 def run(self): 
 print('running') 

# 列出类的所有成员和属性 
 dir(Foo) 
 ['__class__', 
 '__delattr__', 
 '__dict__', 
 '__dir__', 
 '__doc__', 
 '__eq__', 
 '__format__', 
 '__ge__', 
 '__getattribute__', 
 '__gt__', 
 '__hash__', 
 '__init__', 
 '__init_subclass__', 
 '__le__', 
 '__lt__', 
 '__module__', 
 '__ne__', 
 '__new__', 
 '__reduce__', 
 '__reduce_ex__', 
 '__repr__', 
 '__setattr__', 
 '__sizeof__', 
 '__str__', 
 '__subclasshook__', 
 '__weakref__', 
 'run'] 
 # 类的注释 
 Foo.__doc__ 
 # 'this is test class' 
 # 类自定义属性 
 Foo.__dict__ 
 mappingproxy({'__module__': '__main__', 
 '__doc__': 'this is test class', 
 '__init__': <function __main__.Foo.__init__(self, name)>, 
 'run': <function __main__.Foo.run(self)>, 
 '__dict__': <attribute '__dict__' of 'Foo' objects>, 
 '__weakref__': <attribute '__weakref__' of 'Foo' objects>}) 
 # 类的父类 
 Foo.__base__ 
 # 类的名字 
 Foo.__name__ 

# python类先通过__new__实例化，再调用__init__进行初始化类成员 
 foo = Foo('milk') 

# 类的访问 
 foo.name 
 foo.run() 
 # 可以通过setattr 动态的添加属性 
 def method(): 
 print("cow") 
 setattr(foo, "type", "cow") 
 setattr(foo, "getcow", method) 
 # cow 
 foo.type 
 foo.getcow() 
 # 动态删除属性 delattr 
 delattr(foo, "type") 
 # getattr 获取成员属性 
 if hasattr(foo, "run"): # 判断是否有属性 
 func = getattr(foo, "run") 
 func() 

class Singleton(object): 
 def __new__(cls, *args, **kwargs): 
 if not hasattr(cls, '_instance'): 
 cls._instance = object.__new__(cls) 
 return cls._instance 
 def __init__(self, name): 
 self.name = name 
a = Singleton('name1') 
b = Singleton('name2') 
print(id(a), id(b)) 
print(a.name, b.name) 
# 1689352213112 1689352213112 
# name2 name2 

import importlib 
from operator import methodcaller 
class Foo(): 
 """this is test class""" 
 def __init__(self, name): 
 self.name = name 
 def run(self, info): 
 print('running %s' % info) 
# 类所在的模块，默认情况__main__， 可以通过Foo.__dict__ 中'__module__'获取 
api_module = importlib.import_module('__main__') 
# getattr获取模块中的类， 这里Foo是字符串哦 
clazz = getattr(api_module, 'Foo') 
# 实例化 
params = ["milk"] 
instance = clazz(*params) 
# 方法调用， 方法也是字符串methodcaller(方法名， 方法参数) 
task_result = methodcaller("run", "reflection")(instance) 
# running reflection