python type
Return the type of an object. The return value is a type object. The isinstance() built-in function is recommended for testing the type of an object.
返回对象的类型。返回的对象是一个type类型。推荐使用isinstance()来检测一个对象的类型。
With three arguments, type() functions as a constructor as detailed below.
使用3个参数的时候,type()方法可以作为一个构造器。
Return a new type object. This is essentially a dynamic form of the class statement. The name string is the class name and becomes the __name__ attribute; the bases tuple itemizes the base classes and becomes the __bases__ attribute; and the dict dictionary is the namespace containing definitions for class body and becomes the __dict__ attribute. For example, the following two statements create identical type objects:
返回一个新的类型对象。从本质来说是一种类的动态声明。
name 参数是class的名称,也是 __name__属性的值
bases 元组列出了这个类的父类,成为了__bases__属性的值
dict 包含了类体的定义,成为 __dict__属性
下面是一个案例:
>>> class X(object):
... a = 1
...
>>> X = type('X', (object,), dict(a=1))
#----------------------------------------------------------------------------
也就是说这个type可以在运行时生成我们定制的类
自己来试一试:
使用type来判断对象类型是否相同:
1 ############### In [8]: a = '1' In [9]: b = type(a) In [10]: isinstance('3',b) Out[10]: True In [11]: isinstance([],b) Out[11]: False 使用type来动态创建类 2################# In [12]: Pycon = type('Pycon',(object,),{'age':20}) In [13]: type(Pycon) Out[13]: type In [14]: Pycon.age Out[14]: 20 In [15]: Pycon.__name__ Out[15]: 'Pycon' 3################# In [20]: fun = lambda x: x+1 In [21]: ClaFun = type('ClaFun',(object,),{'add':fun }) In [22]: type(ClaFun.add) Out[22]: instancemethod In [26]: a = ClaFun() In [27]: a.add(3) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-27-bebdff6e9b30> in <module>() ----> 1 a.add(3) TypeError: <lambda>() takes exactly 1 argument (2 given) #---但是调用不行,缺少了一个self参数 4################# In [29]: fun = lambda self,x: x+1 In [30]: ClaFun = type('ClaFun',(object,),{'add':fun }) In [31]: a = ClaFun() In [32]: a.add(3) Out[32]: 4
这样就行了,根据条件动态创建类应该很有用处。