我想模仿一个普通的python列表，除非通过切片添加或删除元素，我想“保存”列表。这可能吗？这是我的尝试，但它永远不会打印“保存”。
class InterceptedList(list):
def addSave(func):
def newfunc(self, *args):
func(self, *args)
print 'saving'
return newfunc
__setslice__ = addSave(list.__setslice__)
__delslice__ = addSave(list.__delslice__)
>>> l = InterceptedList()
>>> l.extend([1,2,3,4])
>>> l
[1, 2, 3, 4]
>>> l[3:] = [5] # note: 'saving' is not printed
>>> l
[1, 2, 3, 5]
这适用于append和extend等其他方法，而不适用于切片操作。
编辑：真正的问题是我使用的是Jython而不是Python而忘了它。对这个问题的评论是正确的。这段代码在Python（2.6）中运行良好。但是，代码和答案都适用于Jython。
答案 0 :(得分：5)
__getslice__(), __setslice__() and __delslice__() were killed.
The syntax a[i:j] now translates to a.__getitem__(slice(i, j))
(or __setitem__() or __delitem__(), when used as an assignment
or deletion target, respectively).
答案 1 :(得分：5)
“setslice”和“delslice”已弃用，如果你想进行拦截，你需要处理传递给“setitem”和“delitem”的python切片对象。如果你想要截断两个切片和普通访问，这个代码在python 2.6.2中完美地运行。
class InterceptedList(list):
def addSave(func):
def newfunc(self, *args):
func(self, *args)
print 'saving'
return newfunc
def __setitem__(self, key, value):
print 'saving'
list.__setitem__(self, key, value)
def __delitem__(self, key):
print 'saving'
list.__delitem__(self, key)
答案 2 :(得分：5)
这是足够的推测。让我们开始使用事实而不是吗？ 据我所知，底线是您必须覆盖这两组方法。
如果要实现撤消/重做，您可能应该尝试使用撤消堆栈和可以执行（）/撤消（）操作的操作集。
import profile
import sys
print sys.version
class InterceptedList(list):
def addSave(func):
def newfunc(self, *args):
func(self, *args)
print 'saving'
return newfunc
__setslice__ = addSave(list.__setslice__)
__delslice__ = addSave(list.__delslice__)
class InterceptedList2(list):
def __setitem__(self, key, value):
print 'saving'
list.__setitem__(self, key, value)
def __delitem__(self, key):
print 'saving'
list.__delitem__(self, key)
print("------------Testing setslice------------------")
l = InterceptedList()
l.extend([1,2,3,4])
profile.run("l[3:] = [5]")
profile.run("l[2:6] = [12, 4]")
profile.run("l[-1:] = [42]")
profile.run("l[::2] = [6,6]")
print("-----------Testing setitem--------------------")
l2 = InterceptedList2()
l2.extend([1,2,3,4])
profile.run("l2[3:] = [5]")
profile.run("l2[2:6] = [12,4]")
profile.run("l2[-1:] = [42]")
profile.run("l2[::2] = [6,6]")
C:\Users\wuu-local.pyza\Desktop>c:\jython2.5.0\jython.bat intercept.py
2.5.0 (Release_2_5_0:6476, Jun 16 2009, 13:33:26)
[Java HotSpot(TM) Client VM (Sun Microsystems Inc.)]
------------Testing setslice------------------
saving
3 function calls in 0.035 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.000 0.000 0.000 0.000 intercept.py:9(newfunc)
1 0.034 0.034 0.035 0.035 profile:0(l[3:] = [5])
0 0.000 0.000 profile:0(profiler)
saving
3 function calls in 0.005 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.001 0.001 <string>:0(<module>)
1 0.001 0.001 0.001 0.001 intercept.py:9(newfunc)
1 0.004 0.004 0.005 0.005 profile:0(l[2:6] = [12, 4])
0 0.000 0.000 profile:0(profiler)
saving
3 function calls in 0.012 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.000 0.000 0.000 0.000 intercept.py:9(newfunc)
1 0.012 0.012 0.012 0.012 profile:0(l[-1:] = [42])
0 0.000 0.000 profile:0(profiler)
2 function calls in 0.004 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.004 0.004 0.004 0.004 profile:0(l[::2] = [6,6])
0 0.000 0.000 profile:0(profiler)
-----------Testing setitem--------------------
2 function calls in 0.004 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.004 0.004 0.004 0.004 profile:0(l2[3:] = [5])
0 0.000 0.000 profile:0(profiler)
2 function calls in 0.006 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.006 0.006 0.006 0.006 profile:0(l2[2:6] = [12,4])
0 0.000 0.000 profile:0(profiler)
2 function calls in 0.004 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 <string>:0(<module>)
1 0.004 0.004 0.004 0.004 profile:0(l2[-1:] = [42])
0 0.000 0.000 profile:0(profiler)
saving
3 function calls in 0.007 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.002 0.002 <string>:0(<module>)
1 0.001 0.001 0.001 0.001 intercept.py:20(__setitem__)
1 0.005 0.005 0.007 0.007 profile:0(l2[::2] = [6,6])
0 0.000 0.000 profile:0(profiler)
C:\Users\wuu-local.pyza\Desktop>python intercept.py
2.6 (r26:66721, Oct 2 2008, 11:35:03) [MSC v.1500 32 bit (Intel)]
------------Testing setslice------------------
saving
4 function calls in 0.002 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.002 0.002 0.002 0.002 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 intercept.py:9(newfunc)
1 0.000 0.000 0.002 0.002 profile:0(l[3:] = [5])
0 0.000 0.000 profile:0(profiler)
saving
4 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 intercept.py:9(newfunc)
1 0.000 0.000 0.000 0.000 profile:0(l[2:6] = [12, 4])
0 0.000 0.000 profile:0(profiler)
saving
4 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 intercept.py:9(newfunc)
1 0.000 0.000 0.000 0.000 profile:0(l[-1:] = [42])
0 0.000 0.000 profile:0(profiler)
3 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 profile:0(l[::2] = [6,6])
0 0.000 0.000 profile:0(profiler)
-----------Testing setitem--------------------
3 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 profile:0(l2[3:] = [5])
0 0.000 0.000 profile:0(profiler)
3 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 profile:0(l2[2:6] = [12,4])
0 0.000 0.000 profile:0(profiler)
3 function calls in 0.000 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.000 0.000 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 profile:0(l2[-1:] = [42])
0 0.000 0.000 profile:0(profiler)
saving
4 function calls in 0.003 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 0.000 0.000 :0(setprofile)
1 0.000 0.000 0.003 0.003 <string>:1(<module>)
1 0.002 0.002 0.002 0.002 intercept.py:20(__setitem__)
1 0.000 0.000 0.003 0.003 profile:0(l2[::2] = [6,6])
0 0.000 0.000 profile:0(profiler)
答案 3 :(得分：4)
调用__getslice__和__setslice__的情况非常狭窄。具体而言，切片仅在使用常规切片时发生，其中第一个和最终元素仅提及一次。对于任何其他切片语法，或根本没有切片，将调用__getitem__或__setitem__。