我想扩展类“list”的功能,并为事件添加自定义处理程序:“添加新项目到列表”和“从列表中删除项目”。对于这个任务我不想使用组合,更好的是继承。Python:扩展列表的正确方式
什么,我试图做的事:
class ExtendedList(list):
def append(self, obj):
super(ExtendedList, self).append(obj)
print('Added new item')
def extend(self, collection):
if (hasattr(collection, '__iter__') or hasattr(collection, '__getitem__')) and len(collection)>0:
for item in collection:
self.append(item)
def insert(self, index, obj):
super(ExtendedList, self).insert(index, obj)
print('Added new item')
def remove(self, value):
super(ExtendedList, self).remove(value)
print('Item removed')
但它不能正常工作。我无法捕捉所有添加和删除事件。例如:
collection = ExtendedList()
collection.append('First item')
# Out: "Added new item\n"; collection now is: ['First item']
collection.extend(['Second item', 'Third item'])
# Out: "Added new item\nAdded new item\n"; collection now is: ['First item', 'Second item', 'Third item']
collection += ['Four item']
# Don't out anythink; collection now is: ['First item', 'Second item', 'Third item', 'Four item']
collection.remove('First item')
# Out: "Item removed\n"; collection now is: ['Second item', 'Third item', 'Four item']
del collection[0:2]
# Don't out anythink; collection now is: ['Four item']
collection *= 3
# Don't out anythink; collection now is: ['Four item', 'Four item', 'Four item']
什么是正确的方式来扩展我的情况类“列表”?感谢帮助。
在这里定义列表的子类不是一个好主意。相反,你应该倾向于继承聚合 – gefei
这些都做不同的事情,所以使用一个更适合你想要完成的事情? – brandonscript
你已经展示了会发生什么,但是它有什么问题?你想要发生什么? – nmichaels