How would I create a custom list class in python?

Question

I would like to write a custom list class in Python (let\'s call it MyCollection) where I can eventually call:

for x in myCollectionInstance:
           


        

Answer 1

I like to subclass MutableSequence, as recommended by Alex Martelli. This works well for me, particularly when I need to add custom methods on top of the list I'm building.

try:
    # Python 3
    from collections.abc import MutableSequence
except ImportError:
    # Python 2.7
    from collections import MutableSequence

class MyList(MutableSequence):
    """A container for manipulating lists of hosts"""
    def __init__(self, data=None):
        """Initialize the class"""
        super(MyList, self).__init__()
        if (data is not None):
            self._list = list(data)
        else:
            self._list = list()

    def __repr__(self):
        return "<{0} {1}>".format(self.__class__.__name__, self._list)

    def __len__(self):
        """List length"""
        return len(self._list)

    def __getitem__(self, ii):
        """Get a list item"""
        return self._list[ii]

    def __delitem__(self, ii):
        """Delete an item"""
        del self._list[ii]

    def __setitem__(self, ii, val):
        # optional: self._acl_check(val)
        self._list[ii] = val

    def __str__(self):
        return str(self._list)

    def insert(self, ii, val):
        # optional: self._acl_check(val)
        self._list.insert(ii, val)

    def append(self, val):
        self.insert(len(self._list), val)

if __name__=='__main__':
    foo = MyList([1,2,3,4,5])
    foo.append(6)
    print foo  #