Solution #1099
Solution #1099
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Review Summary
I am requesting changes because there are still two checklist violations that are considered core requirements, not just style preferences. First, the checklist explicitly requires that any method adding or deleting an item must update self.length, but your implementation uses self.size instead; you should rename the attribute to self.length (initialized where self.size currently is) and update all its uses, including increments, resets during resize, and in __len__ so that __len__ returns self.length [CHECKLIST ITEM #3]. Second, on line 70 you raise KeyError(key) without a descriptive message; the checklist requires providing a message when raising exceptions, so change this to include context, e.g. raise KeyError(f"Key not found: {key}") or similar [CHECKLIST ITEM #1]. Once those are fixed, your Dictionary implementation already meets the functional requirements (Node structure, chaining, __setitem__, __getitem__, __len__, and resizing), so no further mandatory changes are needed. Optional enhancements like adding more dictionary-like methods (clear, get, pop, etc.) and extra tests for collisions/resizing could further strengthen your solution but are not blockers. Overall, you’re very close—addressing the length attribute naming and the KeyError message will bring your code fully in line with the checklist and task requirements.
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Footnotes
app/main.py
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| self.size: int = 0 | ||
| self.table: List[Optional[Node]] = [None] * self.capacity | ||
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| def __len__(self) -> int: | ||
| return self.size | ||
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| def _get_index(self, key_hash: int) -> int: | ||
| return key_hash % self.capacity | ||
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| def __setitem__(self, key: Any, value: Any) -> None: | ||
| # Resize if needed | ||
| if self.size + 1 > self.capacity * self.load_factor: | ||
| self._resize() | ||
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| key_hash = hash(key) | ||
| index = self._get_index(key_hash) | ||
| node = self.table[index] | ||
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| # No collision → save directly | ||
| if node is None: | ||
| self.table[index] = Node(key, value) | ||
| self.size += 1 | ||
| return | ||
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| # Collision → walk linked list | ||
| prev: Optional[Node] = None | ||
| while node: | ||
| if node.key == key: | ||
| node.value = value | ||
| return | ||
| prev = node | ||
| node = node.next | ||
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| # Add new node at end | ||
| prev.next = Node(key, value) | ||
| self.size += 1 | ||
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| def __getitem__(self, key: Any) -> Any: | ||
| key_hash = hash(key) | ||
| index = self._get_index(key_hash) | ||
| node = self.table[index] | ||
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| while node: | ||
| if node.key == key: | ||
| return node.value | ||
| node = node.next | ||
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| raise KeyError(key) | ||
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| def _resize(self) -> None: | ||
| """Double table size and rehash all items.""" | ||
| old_table = self.table | ||
| self.capacity *= 2 | ||
| self.table = [None] * self.capacity | ||
| self.size = 0 # will re-add all nodes |
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This violates the checklist requirement: "in any method that add or delete an item we change self.length" (from the Good example) . The class uses the attribute self.size (initialized on line 23 and updated elsewhere) instead of the expected self.length. Please rename the counter to self.length and update all uses (initialization, increments, resets during resize, and len) so the stored length attribute matches the checklist example and __len__ returns that stored attribute.
app/main.py
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| return node.value | ||
| node = node.next | ||
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| raise KeyError(key) |
There was a problem hiding this comment.
This violates the checklist requirement: "Make sure that you provide a message when an exception raises." . On line 70 the code raises KeyError(key) with no descriptive message. Provide a clearer exception message, for example: raise KeyError(f"Key not found: {key}"), so users/tests get an informative message.
mateacademy-ai-mentor
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Review Summary
I am approving your solution because it cleanly meets all of the core requirements for the custom Dictionary: you implemented a separate Node that stores key, hash, and value, used a list-based hash table with chaining, and correctly provided __setitem__, __getitem__, and __len__ with proper length tracking and descriptive KeyErrors. The resize behavior with an initial capacity and load factor is in place, and collision handling via linked lists per bucket is correctly implemented, so the fundamental functionality is solid and aligned with the checklist.
One area you might improve later is the efficiency of _resize: instead of calling __setitem__ for each node (which can trigger further resizes), you can reinsert directly into the new buckets using node.hash % new_capacity and temporarily skip load-factor checks. You can also make small optimizations by reusing the stored node.hash instead of recomputing hash(key) when moving existing entries. As optional enhancements, consider adding more dict-like methods such as clear, get, pop, __delitem__, update, and __iter__, and write tests that explicitly cover collisions and resizing behavior. Overall, your implementation demonstrates a solid understanding of hash tables and meets the required specification—nice work.
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Footnotes
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