python函数式编程示例

╰+攻爆jí腚メ 2022-05-25 09:12 194阅读 0赞

# 下面的例子是关于调用“从未在类中定义过的函数”
    >>> class X(object):
            def __init__(self, arg1, arg2):
                self.a1 = arg1
                self.b1 = arg2
                print "init"
            def my_default(self):
                print "my default function"
    
    >>> x1 = X(1, 2)
    init
    >>>  x1.func1()   # 从未在类中定义过函数func1()
    ---------------------------------------------------------------------------
    AttributeError                            Traceback (most recent call last)
    <ipython-input-68-40c5f1565149> in <module>()
    ----> 1 x1.func1()
    
    AttributeError: 'X' object has no attribute 'func1'
    
    >>> x1.func2()   # 从未在类中定义过函数func2()
    ---------------------------------------------------------------------------
    AttributeError                            Traceback (most recent call last)
    <ipython-input-69-bf53c3f763a9> in <module>()
    ----> 1 x1.func2()
    
    AttributeError: 'X' object has no attribute 'func2'
    >>> 
    >>> class X(object):
            def __init__(self, arg1, arg2):
                self.a1 = arg1
                self.b1 = arg2
                print "init"
            # 当调用此类中未定义过的函数，且传入了参数时，可以使用不定长参数*args
            def my_default(self, *args):
                print "my default function, you input argument: " + str(args[0])
            # 当调用了不存在方法时，则会调用此 __getattr__
            def __getattr__(self, other_func_name):
                print "your are calling other function:", other_func_name
                return self.my_default
    
    >>> x2 = X(5, 6)
    init
    >>> x2.hello("good morning!")
    your are calling other function: hello
    my default function, you input argument: good morning!
    >>> x2.OK(100,200)
    your are calling other function: OK
    my default function, you input argument: 100
    
    # 高阶函数，函数返回函数
    >>> def my_func(n):
            print "In my_func"
            def inner_func(arg):
                print "In inner_func"
                return n * arg
            return inner_func
    
    >>> intermediate_func = my_func(10)
    In my_func
    >>> intermediate_func(3.5)
    In inner_func
    35.0
    
    # ==========使用装饰器实现单实例设计模式===========
    
    # 装饰器。从本质上说，装饰器本质上也是一个python函数，它的作用是增强其他函数的功能(装饰其他函数)
    >>> def make_singleton(a_class):
            instance_dict = dict()
            def create_single_instance():
                if a_class not in instance_dict:
                    # 当且仅当没有此类的实例时，创建一个此类的实例
                    instance_dict[a_class] = a_class()
                return instance_dict[a_class]
            return create_single_instance
    
    >>> # 使用装饰器，直接放到其他对象的“头上”
    @make_singleton
    >>> class MyClass(object):
            from datetime import datetime
            now_time = str(datetime.now())
            def show_created_time(self):
                return "created time was:", self.now_time
    
    # 尝试创建两个对象
    >>> obj1 = MyClass()
    >>> obj2 = MyClass()
    
    # 通过调用同一个方法查看是否创建于同一个时间点(也就是同一个实例)
    >>> obj1.show_created_time()
    ('created time was:', '2018-05-11 17:10:40.666000')
    >>> obj2.show_created_time()
    ('created time was:', '2018-05-11 17:10:40.666000')
    # 检查是否同一个对象，结果：是
    >>> print id(obj1), id(obj2)
    109425040 109425040

好了，就写到这里，看官们觉得涨知识了，请在文章左侧点个赞 \_