source: utilitiespy/tudelft/utilities/immutablelist/ListWithRemove.py

from __future__ import annotations
from typing import TypeVar, Generic, List
from tudelft.utilities.immutablelist.AbstractImmutableList import AbstractImmutableList
from tudelft.utilities.immutablelist.ImmutableList import ImmutableList
from typing import Set

E = TypeVar('E')

class ListWithRemove(Generic[E], AbstractImmutableList[E]):
        '''
        Creates new list with some elements removed from the list. Immutable    
        @param list     an ImmutableList
        @param removed the removed items. Set to empty set initially.   
        '''

        def __init__(self,  list: ImmutableList[E], removed: Set[int]):
                self._list = list
                self._removedIndices=sorted(frozenset(removed))


        #Override
        def get(self , index:int) ->E :
                return self._list.get(self._realIndex(index))

        def _realIndex(self, index:int) -> int:
                '''
                 @param index
                 @return the real index of an item in the original list. This can be
                         larger than given index because {@link #remvedIndices} are
                         invisible. This operation can become expensive if many items have
                          been removed
                '''
                realIndex:int = index;
                
                # invariant: realIndex has correct value if only removedIndices up to
                # current iteration were in the list.
                for removed in self._removedIndices:
                        if removed > realIndex: 
                                break
                        realIndex += 1

                return realIndex;


        #Override
        def size(self) ->int:
                return self._list.size() - len(self._removedIndices)

        def remove(self, index:int) -> ListWithRemove[E]:
                '''     
                 Remove item at index n
                 
                 @param index index of the element to return
                 @return the element at the specified position in this list before it was
                         removed.
                '''
                removed:Set[int] = set(self._removedIndices)
                removed.add(self._realIndex(index));
                return ListWithRemove(self._list, removed);