类变量与实例变量
Python中类__init__函数外部的所有变量都是类变量，而内部的所有变量都是实例变量。通过检查以下代码，可以更好地理解类变量和实例变量之间的区别
例class MyClass:
stat_elem = 456
def __init__(self):
self.object_elem = 789
c1 = MyClass()c2 = MyClass()# Initial values of both elements
>>> print c1.stat_elem, c1.object_elem
456 789
>>> print c2.stat_elem, c2.object_elem
456 789
# Let's try changing the static element
MyClass.static_elem = 888
>>> print c1.stat_elem, c1.object_elem
888 789
>>> print c2.stat_elem, c2.object_elem
888 789
# Now, let's try changing the object element
c1.object_elem = 777
>>> print c1.stat_elem, c1.object_elem
888 777
>>> print c2.stat_elem, c2.object_elem
888 789
