【Python】MutableSequenceを継承してリスト風クラスを作成する

1class MutableSequence(Sequence):
2    """All the operations on a read-write sequence.
3    Concrete subclasses must provide __new__ or __init__,
4    __getitem__, __setitem__, __delitem__, __len__, and insert().
5    """
6
7    __slots__ = ()
8
9    @abstractmethod
10    def __setitem__(self, index, value):
11        raise IndexError
12
13    @abstractmethod
14    def __delitem__(self, index):
15        raise IndexError
16
17    @abstractmethod
18    def insert(self, index, value):
19        'S.insert(index, value) -- insert value before index'
20        raise IndexError
21
22    def append(self, value):
23        'S.append(value) -- append value to the end of the sequence'
24        self.insert(len(self), value)
25
26    def clear(self):
27        'S.clear() -> None -- remove all items from S'
28        try:
29            while True:
30                self.pop()
31        except IndexError:
32            pass
33
34    def reverse(self):
35        'S.reverse() -- reverse *IN PLACE*'
36        n = len(self)
37        for i in range(n//2):
38            self[i], self[n-i-1] = self[n-i-1], self[i]
39
40    def extend(self, values):
41        'S.extend(iterable) -- extend sequence by appending elements from the iterable'
42        if values is self:
43            values = list(values)
44        for v in values:
45            self.append(v)
46
47    def pop(self, index=-1):
48        '''S.pop([index]) -> item -- remove and return item at index (default last).
49           Raise IndexError if list is empty or index is out of range.
50        '''
51        v = self[index]
52        del self[index]
53        return v
54
55    def remove(self, value):
56        '''S.remove(value) -- remove first occurrence of value.
57           Raise ValueError if the value is not present.
58        '''
59        del self[self.index(value)]
60
61    def __iadd__(self, values):
62        self.extend(values)
63        return self

1from collections.abc import MutableSequence
2# 何も定義しない場合、インスタンス生成時にエラーとなる。最低限必要なメソッドを定義する必要がある
3class MyList(MutableSequence):
4    pass
5
6my_list = MyList()
7# TypeError: Can't instantiate abstract class MyList with abstract methods 
8# __delitem__, __getitem__, __len__, __setitem__, insert

1from collections.abc import MutableSequence
2# __delitem__, __getitem__, __len__, __setitem__, insertを定義
3class MyList(MutableSequence):
4    # __init__がないとself.dataがないため、エラーとなる
5    def __init__(self, initlist=None):
6        self.data = []
7        if initlist is not None:
8            # XXX should this accept an arbitrary sequence?
9            if type(initlist) == type(self.data):
10                self.data[:] = initlist
11            elif isinstance(initlist, UserList):
12                self.data[:] = initlist.data[:]
13            else:
14                self.data = list(initlist)
15
16    def __getitem__(self, i):
17        if isinstance(i, slice):
18            return self.__class__(self.data[i])
19        else:
20            return self.data[i]
21
22    def __delitem__(self, i):
23        del self.data[i]
24
25    def __len__(self):
26        return len(self.data)
27
28    def __setitem__(self, i, item):
29        self.data[i] = item
30
31    def insert(self, i, item):
32        self.data.insert(i, item)
33    # print()でリストの内容を確認するために__repr__を作る
34    def __repr__(self):
35        return repr(self.data)

1my_list = MyList([1, 2, 3])
2print(my_list)
3# __del__
4del my_list[2]
5print(my_list)
6# [1, 2]
7# __setitem__
8my_list[-1] = 4
9print(my_list)
10# [1, 4]
11# insert
12my_list.insert(0, 5)
13print(my_list)
14# [5, 1, 4]
15# __len__
16print(len(my_list))
17# 3
18# __getitem__
19print(my_list[0])
20# 5
21print(my_list[1:])
22# [1, 4]

1# 予め定義されているメソッドも使用可能
2my_list = MyList([1, 2, 3])
3# append
4my_list.append(4)
5print(my_list)
6# [1, 2, 3, 4]
7# extend
8my_list.extend([5])
9print(my_list)
10# [1, 2, 3, 4, 5]
11# __iadd__
12my_list += [6]
13print(my_list)
14# [1, 2, 3, 4, 5, 6]
15my_list.pop()
16print(my_list)
17# [1, 2, 3, 4, 5]
18my_list.remove(5)
19print(my_list)
20# [1, 2, 3, 4]
21my_list.reverse()
22print(my_list)
23# [4, 3, 2, 1]

1from collections.abc import MutableSequence
2# __delitem__, __getitem__, __len__, __setitem__, insertを定義
3class MyList(MutableSequence):
4    # __init__がないとself.dataがないため、エラーとなる
5    def __init__(self, initlist=None):
6        self.data = []
7        if initlist is not None:
8            # XXX should this accept an arbitrary sequence?
9            if type(initlist) == type(self.data):
10                self.data[:] = initlist
11            elif isinstance(initlist, UserList):
12                self.data[:] = initlist.data[:]
13            else:
14                self.data = list(initlist)
15
16    def __getitem__(self, i):
17        if isinstance(i, slice):
18            return self.__class__(self.data[i])
19        else:
20            return self.data[i]
21
22    def __delitem__(self, i):
23        del self.data[i]
24
25    def __len__(self):
26        return len(self.data)
27
28    def __setitem__(self, i, item):
29        self.data[i] = item
30
31    def insert(self, i, item):
32        self.data.insert(i, item)