python类

class a(object):
    #有的地方在语法构成上需要一行语句(相当于c++里的int i=0),但实际上不需要任何操作，这时候可以使用pass
    pass

>>> a
<class '__main__.a'>
>>> a.x

Traceback (most recent call last):
  File "<pyshell#15>", line 1, in <module>
    a.x
AttributeError: type object 'a' has no attribute 'x'
>>> a.x=1
>>> a.x
1
>>> 

class a(object):
    #这里的init左右各有2个下划线
    def __init__(self,m1,m2):
        self.m1 = m1
        self.m2 = m2
        print 'constructor: m1 is %s,m2 is %s' %(m1,m2)
    #这里的self是必需的
    def fun(self):
        print 'test fun()'

>>> b = a('1','2')
constructor: m1 is 1,m2 is 2
>>> b.m1
'1'
>>> b.m2 = '3'
>>> b.m2
'3'
>>> b.fun()
test fun()
要知道一个类有哪些属性
>>> print dir(a)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'fun']
dict返回的是一个字典，它的键(key)是属性名，键值(value）是相应的属性对象的数据值
>>> print a.__dict__
{'__module__': '__main__', '__dict__': <attribute '__dict__' of 'a' objects>, 'fun': <function fun at 0x0000000002ED8048>, '__weakref__': <attribute '__weakref__' of 'a' objects>, '__doc__': None, '__init__': <function __init__ at 0x0000000002ED3F98>}