1  ---
  2  title: Document Writers
  3  id: document-writers-api
  4  description: Writes Documents to a DocumentStore.
  5  slug: "/document-writers-api"
  6  ---
  7  
  8  <a id="document_writer"></a>
  9  
 10  # Module document\_writer
 11  
 12  <a id="document_writer.DocumentWriter"></a>
 13  
 14  ## DocumentWriter
 15  
 16  Writes documents to a DocumentStore.
 17  
 18  ### Usage example
 19  ```python
 20  from haystack import Document
 21  from haystack.components.writers import DocumentWriter
 22  from haystack.document_stores.in_memory import InMemoryDocumentStore
 23  docs = [
 24      Document(content="Python is a popular programming language"),
 25  ]
 26  doc_store = InMemoryDocumentStore()
 27  writer = DocumentWriter(document_store=doc_store)
 28  writer.run(docs)
 29  ```
 30  
 31  <a id="document_writer.DocumentWriter.__init__"></a>
 32  
 33  #### DocumentWriter.\_\_init\_\_
 34  
 35  ```python
 36  def __init__(document_store: DocumentStore,
 37               policy: DuplicatePolicy = DuplicatePolicy.NONE)
 38  ```
 39  
 40  Create a DocumentWriter component.
 41  
 42  **Arguments**:
 43  
 44  - `document_store`: The instance of the document store where you want to store your documents.
 45  - `policy`: The policy to apply when a Document with the same ID already exists in the DocumentStore.
 46  - `DuplicatePolicy.NONE`: Default policy, relies on the DocumentStore settings.
 47  - `DuplicatePolicy.SKIP`: Skips documents with the same ID and doesn't write them to the DocumentStore.
 48  - `DuplicatePolicy.OVERWRITE`: Overwrites documents with the same ID.
 49  - `DuplicatePolicy.FAIL`: Raises an error if a Document with the same ID is already in the DocumentStore.
 50  
 51  <a id="document_writer.DocumentWriter.to_dict"></a>
 52  
 53  #### DocumentWriter.to\_dict
 54  
 55  ```python
 56  def to_dict() -> dict[str, Any]
 57  ```
 58  
 59  Serializes the component to a dictionary.
 60  
 61  **Returns**:
 62  
 63  Dictionary with serialized data.
 64  
 65  <a id="document_writer.DocumentWriter.from_dict"></a>
 66  
 67  #### DocumentWriter.from\_dict
 68  
 69  ```python
 70  @classmethod
 71  def from_dict(cls, data: dict[str, Any]) -> "DocumentWriter"
 72  ```
 73  
 74  Deserializes the component from a dictionary.
 75  
 76  **Arguments**:
 77  
 78  - `data`: The dictionary to deserialize from.
 79  
 80  **Raises**:
 81  
 82  - `DeserializationError`: If the document store is not properly specified in the serialization data or its type cannot be imported.
 83  
 84  **Returns**:
 85  
 86  The deserialized component.
 87  
 88  <a id="document_writer.DocumentWriter.run"></a>
 89  
 90  #### DocumentWriter.run
 91  
 92  ```python
 93  @component.output_types(documents_written=int)
 94  def run(documents: list[Document], policy: Optional[DuplicatePolicy] = None)
 95  ```
 96  
 97  Run the DocumentWriter on the given input data.
 98  
 99  **Arguments**:
100  
101  - `documents`: A list of documents to write to the document store.
102  - `policy`: The policy to use when encountering duplicate documents.
103  
104  **Raises**:
105  
106  - `ValueError`: If the specified document store is not found.
107  
108  **Returns**:
109  
110  Number of documents written to the document store.
111  
112  <a id="document_writer.DocumentWriter.run_async"></a>
113  
114  #### DocumentWriter.run\_async
115  
116  ```python
117  @component.output_types(documents_written=int)
118  async def run_async(documents: list[Document],
119                      policy: Optional[DuplicatePolicy] = None)
120  ```
121  
122  Asynchronously run the DocumentWriter on the given input data.
123  
124  This is the asynchronous version of the `run` method. It has the same parameters and return values
125  but can be used with `await` in async code.
126  
127  **Arguments**:
128  
129  - `documents`: A list of documents to write to the document store.
130  - `policy`: The policy to use when encountering duplicate documents.
131  
132  **Raises**:
133  
134  - `ValueError`: If the specified document store is not found.
135  - `TypeError`: If the specified document store does not implement `write_documents_async`.
136  
137  **Returns**:
138  
139  Number of documents written to the document store.