> ## Documentation Index
> Fetch the complete documentation index at: https://docs.camel-ai.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Camel.memories.blocks.chat history block

<a id="camel.memories.blocks.chat_history_block" />

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock" />

## ChatHistoryBlock

```python theme={"system"}
class ChatHistoryBlock(MemoryBlock):
```

An implementation of the :obj:`MemoryBlock` abstract base class for
maintaining a record of chat histories.

This memory block helps manage conversation histories with a key-value
storage backend, either provided by the user or using a default
in-memory storage. It offers a windowed approach to retrieving chat
histories, allowing users to specify how many recent messages they'd
like to fetch.

**Parameters:**

* **storage** (BaseKeyValueStorage, optional): A storage mechanism for storing chat history. If `None`, an :obj:`InMemoryKeyValueStorage` will be used. (default: :obj:`None`)
* **keep\_rate** (float, optional): In historical messages, the score of the last message is 1.0, and with each step taken backward, the score of the message is multiplied by the `keep_rate`. Higher `keep_rate` leads to high possibility to keep history messages during context creation. (default: :obj:`0.9`)

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.__init__" />

### **init**

```python theme={"system"}
def __init__(
    self,
    storage: Optional[BaseKeyValueStorage] = None,
    keep_rate: float = 0.9
):
```

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.retrieve" />

### retrieve

```python theme={"system"}
def retrieve(self, window_size: Optional[int] = None):
```

Retrieves records with a proper size for the agent from the memory
based on the window size or fetches the entire chat history if no
window size is specified.

**Parameters:**

* **window\_size** (int, optional): Specifies the number of recent chat messages to retrieve. If not provided, the entire chat history will be retrieved. (default: :obj:`None`)

**Returns:**

List\[ContextRecord]: A list of retrieved records.

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.write_records" />

### write\_records

```python theme={"system"}
def write_records(self, records: List[MemoryRecord]):
```

Writes memory records to the memory. Additionally, performs
validation checks on the messages.

**Parameters:**

* **records** (List\[MemoryRecord]): Memory records to be added to the memory.

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.clear" />

### clear

```python theme={"system"}
def clear(self):
```

Clears all chat messages from the memory.

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.pop_records" />

### pop\_records

```python theme={"system"}
def pop_records(self, count: int):
```

Removes the most recent records from the memory.

**Parameters:**

* **count** (int): Number of records to remove from the end of the conversation history. A value of 0 results in no changes.

**Returns:**

List\[MemoryRecord]: The removed records in chronological order.

<a id="camel.memories.blocks.chat_history_block.ChatHistoryBlock.remove_records_by_indices" />

### remove\_records\_by\_indices

```python theme={"system"}
def remove_records_by_indices(self, indices: List[int]):
```

Removes records at specified indices from the memory.

**Parameters:**

* **indices** (List\[int]): List of indices to remove. Indices are positions in the current record list (0-based). System/developer messages at index 0 are protected and will not be removed.

**Returns:**

List\[MemoryRecord]: The removed records in their original order.