test.py中的代码:
class Base(object):
def __init__(self, l=[]):
self.l = l
def add(self, num):
self.l.append(num)
def remove(self, num):
self.l.remove(num)
class Derived(Base):
def __init__(self, l=[]):
super(Derived, self).__init__(l)
Python命令行会话:
Python 2.6.5 (r265:79063, Apr 1 2010, 05:22:20)
[GCC 4.4.3 20100316 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import test
>>> a = test.Derived()
>>> b = test.Derived()
>>> a.l
[]
>>> b.l
[]
>>> a.add(1)
>>> a.l
[1]
>>> b.l
[1]
>>> c = test.Derived()
>>> c.l
[1]
我原本期望的是 "类似于C++" 的行为,即每个派生对象都包含其自己的基类实例。这仍然是这种情况吗?为什么每个对象看起来共享相同的列表实例?
def __init__(self, arg=None): self.arg = arg or []
- Olivier Maurel