Subclass builtin List

python list subclass built-in
SapphireSun picture SapphireSun · Feb 10, 2010 · Viewed 6.9k times · Source

I want to subclass the list type and have slicing return an object of the descendant type, however it is returning a list. What is the minimum code way to do this?

If there isn't a neat way to do it, I'll just include a list internally which is slightly more messy, but not unreasonable.

My code so far:

class Channel(list):
    sample_rate = 0
    def __init__(self, sample_rate, label=u"", data=[]):
        list.__init__(self,data)
        self.sample_rate = sample_rate
        self.label = label

    @property
    def nyquist_rate(self):
        return float(self.sample_rate) / 2.0

Answer

fortran picture fortran · Feb 10, 2010

I guess you should override the __getslice__ method to return an object of your type...

Maybe something like the following?

class MyList(list):
    #your stuff here

    def __getslice__(self, i, j):
        return MyList(list.__getslice__(self, i, j))

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