Python单利模式，简单工厂实现，import自定义模块

import mypackage.ZString as zs
'''
单利模式
'''

class User(object):
__instance = None

def __init__(self, name, age):
    self.name = name
    self.age = age
    print('name=%s,age=%s' % (self.name, self.age))

def __new__(cls, name, age):
    if not cls.__instance:
        cls.__instance = object.__new__(cls)
    return cls.__instance

u1 = User('tom', 18)
u2 = User('jack', 28)

print(u1 == u2)
print(id(u1))
print(id(u2))

'''
工厂模式
'''

class Person(object):
def init(self, name):
self.name = name

def work(self, axe_type):
    print('%s开始工作了' % self.name)
    # axe=StoneAxe('花岗岩')
    # axe=SteelAxe('加爵')
    axe = Factory.get_axe(axe_type)
    if not axe == None:
        axe.cut_tree()

class Axe(object):
def init(self, name):
self.name = name

def cut_tree(self):
    print('%s进行砍树了' % self.name)

class StoneAxe(Axe):
def cut_tree(self):
super().cut_tree() # 子类调用父类方法
print('使用石头做的斧头砍树')

class SteelAxe(Axe):

def cut_tree(self):
    super().cut_tree()  # 子类调用父类方法
    print('使用钢铁做的斧头砍树')

class Factory(object):

静态简单工厂方法

@staticmethod
def get_axe(axe_type):
    if axe_type == "stone":
        return StoneAxe('花岗岩')
    elif axe_type == "steel":
        return SteelAxe('加爵')
    else:
        print('你输入错误吧')

p = Person('张三')
p.work('steel')

def get_str():
s=None
print(zs.isnull(s))

get_str()

字符串为None时为True，为空时也True，否则为False

def isnull(str):
if not str:
return True
elif str.strip() == '':
return True
else:
return False

if name == 'main':
t=None
print(isnull(t))