Harrison/add source column (#1784)

Co-authored-by: Brian Graham <46691715+briangrahamww@users.noreply.github.com>
Co-authored-by: briangrahamww <brian.graham@ww.com>

langchain/document_loaders/csv_loader.py

@@ -11,6 +11,13 @@ class CSVLoader(BaseLoader):
     Each document represents one row of the CSV file. Every row is converted into a
     key/value pair and outputted to a new line in the document's page_content.
 
+    The source for each document loaded from csv is set to the value of the
+    `file_path` argument for all doucments by default.
+    You can override this by setting the `source_column` argument to the
+    name of a column in the CSV file.
+    The source of each document will then be set to the value of the column
+    with the name specified in `source_column`.
+
     Output Example:
         .. code-block:: txt
 
@@ -19,8 +26,14 @@ class CSVLoader(BaseLoader):
             column3: value3
     """
 
-    def __init__(self, file_path: str, csv_args: Optional[Dict] = None):
+    def __init__(
+        self,
+        file_path: str,
+        source_column: Optional[str] = None,
+        csv_args: Optional[Dict] = None,
+    ):
         self.file_path = file_path
+        self.source_column = source_column
         if csv_args is None:
             self.csv_args = {
                 "delimiter": ",",
@@ -35,13 +48,13 @@ class CSVLoader(BaseLoader):
         with open(self.file_path, newline="") as csvfile:
             csv = DictReader(csvfile, **self.csv_args)  # type: ignore
             for i, row in enumerate(csv):
-                docs.append(
-                    Document(
-                        page_content="\n".join(
-                            f"{k.strip()}: {v.strip()}" for k, v in row.items()
-                        ),
-                        metadata={"source": self.file_path, "row": i},
-                    )
-                )
+                content = "\n".join(f"{k.strip()}: {v.strip()}" for k, v in row.items())
+                if self.source_column is not None:
+                    source = row[self.source_column]
+                else:
+                    source = self.file_path
+                metadata = {"source": source, "row": i}
+                doc = Document(page_content=content, metadata=metadata)
+                docs.append(doc)
 
         return docs