小知识点

1.文档字符串（用于函数注释）使用help(函数名.__doc__())函数可以查看注释内容

def func(a,b):
    """
    用于比较两个数的大小
    :param a:
    :param b:
    :return:
    """
    if a>b:
        print("最大：%d"%a)
    else:
        print("最大：%d"%b)


func(5,10)
help(func.__doc__)  # 查看注释内容

# No Python documentation found for '用于比较两个数的大小\n :param a:\n :param b:\n :return:'.
# Use help() to get the interactive help utility.
# Use help(str) for help on the str class.

 2.查看局部变量和全局变量，使用locals()和globals()

a = 3

def func():
    b = 10
    print(b*10)
    global a
    a = 300

    print(locals())  # {'b': 10}  

　　 print(globals()) 

# {'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001FB793965C0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__file__': 'E:/代码库/Mysite/1-1.py', '__cached__': None, 'a': 300, 'func': <function func at 0x000001FB7934C268>}

func()

 3.浅拷贝和深拷贝

浅拷贝不拷贝子对象

4.单例模式

class Singleton:
    __instance = None

    def __new__(cls, *args, **kwargs):
        if not cls.__instance:
            cls.__instance = super().__new__(cls)
            # cls.__instance = object.__new__(cls)
        return cls.__instance


s1 = Singleton()
s2 = Singleton()
print(id(s1))    # 2018028512928
print(id(s2))    # 2018028512928