Python重载列表索引错误

Question

I am trying to overload the [] operator for a list to work like a circular list.

class circularList(list):
    def __init__(self, *args):
        list.__init__(self,args)

    def __getitem__(self, key):
        return list.__getitem__(self, key%self.length)

    def __setitem__(self, key, value):
        return list.__setitem__(self, key%self.length, value)

When running this code in the sage terminal, I get the following error:

TypeError: Error when calling the metaclass bases
    list() takes at most 1 argument (3 given)
sage:     def __getitem__(self, key):
....:             return list.__getitem__(self, key%self.length)
....:     
sage:     def __setitem__(self, key, value):
....:             return list.__setitem__(self, key%self.length, value)

This would be used as follows:

circle = circularlist([1,2,3,4])

Does anyone happen to know what I am doing wrong?

Answer 1

With minor fixes, this works for me using Python 2.7.1:

class circularList(list):
    def __init__(self, *args):
        list.__init__(self,args)

    def __getitem__(self, key):
        return list.__getitem__(self, key%len(self))        # Fixed self.length

    def __setitem__(self, key, value):
        return list.__setitem__(self, key%len(self), value) # Fixed self.length

circle = circularList(1,2,3,4)                              # Fixed uppercase 'L'
                                                            # pass values are argument 
                                                            # (not wrapped in a list)
print circle
for i in range(0,10):
    print i,circle[i]

Producing:

[1, 2, 3, 4]
0 1
1 2
2 3
3 4
4 1
5 2
6 3
7 4
8 1
9 2

---

BTW, are you aware of itertools.cycle ?