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。它是一类在运行时可以改变其结构的语言：例如新的函数、对象、甚至代码可以被引进，已有的函数可以被删除或是其他结构上的变化。动态语言目前非常具有活力。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？这其实是动态语言惹的“祸”！【博主以前玩的是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，但是人还有性别啊！如果这个类不是你写的是不是你会尝试访问性别这个属性呢？
>>> P.sexuality = "male" >>> P.sexuality 'male' >>>
这时候就发现问题了，我们定义的类里面没有sexuality这个属性啊！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！我们再看下一个例子
>>> P1 = Person("Wave", "25")
>>> P1.sexuality
Traceback (most recent call last):
File "<pyshell#21>", line 1, in <module>
P1.sexuality
AttributeError: Person instance has no attribute 'sexuality'
>>>
我们尝试打印P1.sexuality，发现报错，P1没有sexuality这个属性！----给P这个实例绑定属性对P1这个实例不起作用！
那我们要给所有的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.sexuality
None
>>>
我们直接给Person绑定sexuality这个属性，重行实例化P1后，P1就有sexuality这个属性了！
那么function呢？怎么绑定？
>>> class Person():
def __init__(self, name = None, age = None):
self.name = name
self.age = age
def 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，但是怎么删除呢？
请看以下例子首先给的是属性的真删：
>>> P.name
'The_Third_Wave'
>>> P.sex
Traceback (most recent call last):
File "<pyshell#32>", line 1, in <module>
P.sex
AttributeError: Person instance has no attribute 'sex'
>>> setattr(P, "sex", "male") # 増
>>> P.sex
'male'
>>> delattr(P, "name") # 删
>>> P.name
Traceback (most recent call last):
File "<pyshell#36>", line 1, in <module>
P.name
AttributeError: Person instance has no attribute 'name'
>>>
添加方法呢？
>>> class Person():
def __init__(self, name = None, age = None):
self.name = name
self.age = age
def 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
>>>
删除
>>> 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'
>>>
通过以上例子可以得出一个结论：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！
那么怎么避免这种情况呢？请使用__slots__，但是我的是2.7.6版本，测试是不行的！代码如下：
>>> 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.sex
Traceback (most recent call last):
File "<pyshell#3>", line 1, in <module>
P.sex
AttributeError: Person instance has no attribute 'sex'
>>> P.sex = "male"
>>>
具体原因是什么呢，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 = name
AttributeError: '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"请注意这儿参数和上面有个例子不一样哦", 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！
暂时写到这，不定期更新ing...
关于slots的demo原文：https://docs.python.org/2/reference/datamodel.html?highlight=__slots__#__slots__
本文由@The_Third_Wave原创。不定期更新，有错误请指正。
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