为什么说Python是一门动态语言--Python的魅力，,
为什么说Python是一门动态语言--Python的魅力，,
动态语言的定义：动态编程语言是高级程序设计语言的一个类别。在计算机科学领域已被广泛应用。它是一类在执行时能够改变其结构的语言：比如新的函数、对象、甚至代码能够被引进。已有的函数能够被删除或是其它结构上的变化。动态语言眼下很具有活力。众所周知的ECMAScript（JavaScript）便是一个动态语言，除此之外如PHP、Ruby、Python等也都属于动态语言，而C、C++等语言则不属于动态语言。
----来自维基百科
你是不是有过给class里面变量赋值却发现程序没达到自己预期结果的遭遇？是不是本来赋值给class.abc却赋给了class.abd？这事实上是动态语言惹的“祸”！【博主曾经玩的是java】我们先来试着玩一玩
>>> class Person():def __init__(self, name = None, age = None): self.name = name self.age = age >>> P = Person("The_Third_Wave", "24")>>> 在这里。我们定义了1个类Person。在这个类里。定义了两个初始属性name和age，可是人还有性别啊。假设这个类不是你写的是不是你会尝试訪问性别这个属性呢？
>>> P.sexuality = "male">>> P.sexuality‘male‘>>> 怎么回事呢？这就是动态语言的魅力和坑！
这里实际上就是动态给实例绑定属性！所以博主“当年”从java转python被“坑”（无知啊）过！我们再看下一个样例
>>> P1 = Person("Wave", "25")>>> P1.sexualityTraceback (most recent call last): File "<pyshell#21>", line 1, in <module> P1.sexualityAttributeError: Person instance has no attribute ‘sexuality‘>>> 那我们要给全部的Person的实例加上sexuality属性怎么办呢？答案就是直接给Person绑定属性！
>>>> Person.sexuality = None>>> P1 = Person("Wave", "25")>>> print P1.sexualityNone>>> 那么function呢？怎么绑定？
>>> class Person():def __init__(self, name = None, age = None): self.name = name self.age = agedef eat(self): print "eat food" >>> def run(self, speed):print "Keeping moving, the speed is %s km/h" %speed>>> P = Person("The_Third_Wave", "24")>>> KeyboardInterrupt>>> P.run()Traceback (most recent call last): File "<pyshell#5>", line 1, in <module> P.run()AttributeError: Person instance has no attribute ‘run‘>>> P.eat()eat food>>> import types>>> Person.run = types.MethodType(run, None, Person)>>> P.run(180)Keeping moving, the speed is 180 km/h>>> 绑定我们了解了，可是怎么删除呢？
请看下面样例首先给的是属性的真删：
>>> P.name‘The_Third_Wave‘>>> P.sexTraceback (most recent call last): File "<pyshell#32>", line 1, in <module> P.sexAttributeError: Person instance has no attribute ‘sex‘>>> setattr(P, "sex", "male") # 増>>> P.sex‘male‘>>> delattr(P, "name") # 删>>> P.nameTraceback (most recent call last): File "<pyshell#36>", line 1, in <module> P.nameAttributeError: Person instance has no attribute ‘name‘>>> 加入方法呢？
>>> class Person():def __init__(self, name = None, age = None): self.name = name self.age = agedef eat(self): print "eat food" >>> P = Person("The_Third_Wave", "24")>>> P.eat()eat food>>> P.run()Traceback (most recent call last): File "<pyshell#41>", line 1, in <module> P.run()AttributeError: Person instance has no attribute ‘run‘>>> def run(self, speed):print "Keeping moving, the speed is %s" %speed>>> setattr(P, "run", run)>>> P.run(360)Traceback (most recent call last): File "<pyshell#45>", line 1, in <module> P.run(360)TypeError: run() takes exactly 2 arguments (1 given)>>> P.run(1, 360)Keeping moving, the speed is 360>>> >>> delattr(P, "run")>>> P.run()Traceback (most recent call last): File "<pyshell#48>", line 1, in <module> P.run()AttributeError: Person instance has no attribute ‘run‘>>> 通过以上样例能够得出一个结论：相对于动态语言，静态语言具有严谨性！
所以。玩动态语言的时候，小心动态的坑！
那么怎么避免这样的情况呢？请使用__slots__。可是我的是2.7.6版本号，測试是不行的。代码例如以下：
>>> class Person():__slots__ = ("location", "run")def __init__(self, name = None, age = None): self.name = name self.age = age def eat(self): print "eat food" >>> P = Person()>>> P.sexTraceback (most recent call last): File "<pyshell#3>", line 1, in <module> P.sexAttributeError: Person instance has no attribute ‘sex‘>>> P.sex = "male">>> 详细原因是什么呢，本来是准备请等待更新：ing...的
BUT。我多写了个object就出来了。。。
这可真是个神坑！soga！
>>> class Person(object):__slots__ = ("location", "run")def __init__(self, name = None, age = None): self.name = name self.age = age def eat(self): print "eat food" >>> P = Person()Traceback (most recent call last): File "<pyshell#12>", line 1, in <module> P = Person() File "<pyshell#11>", line 5, in __init__ self.name = nameAttributeError: ‘Person‘ object has no attribute ‘name‘ # 顺便还发现了个注意事项：要预先定义的属性也要写到tuple里面！>>> class Person(object):__slots__ = ("name", "age", "eat", "location", "run")def __init__(self, name = None, age = None): self.name = name self.age = age def eat(self): print "eat food" >>> P = Person()>>> P.sex = "male"Traceback (most recent call last): File "<pyshell#16>", line 1, in <module> P.sex = "male"AttributeError: ‘Person‘ object has no attribute ‘sex‘>>> P.location = "china">>> P.location‘china‘>>> def run(self, speed):print "Keeping moving, the speed is %s km/h" %speed>>> setattr(P, "run", run)>>> P.run(u"请注意这儿參数和上面有个样例不一样哦", 720)Keeping moving, the speed is 720 km/h>>>
顺便还发现了个注意事项：要预先定义的属性也要写到tuple里面！
临时写到这，不定期更新ing...关于slots的demo原文：https://docs.python.org/2/reference/datamodel.html?
highlight=__slots__#__slots__
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为什么说Python是一门动态语言--Python的魅力
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