FIX: Fix batch download range handling

Author: cjdsellers

databento/historical/api/batch.py

@@ -290,6 +290,7 @@ def _download_file(
         ]
 
         headers: Dict[str, str] = self._headers.copy()
+        mode = "wb"
 
         # Check if file already exists in partially downloaded state
         if os.path.isfile(output_path):
@@ -298,6 +299,7 @@ def _download_file(
                 # Make range request for partial download,
                 # will be from next byte to end of file.
                 headers["Range"] = f"bytes={existing_size}-{filesize - 1}"
+                mode = "ab"
 
         with requests.get(
             url=self._base_url + ".download",
@@ -309,6 +311,6 @@ def _download_file(
         ) as response:
             check_http_error(response)
 
-            with open(output_path, mode="wb") as f:
+            with open(output_path, mode=mode) as f:
                 for chunk in response.iter_content():
                     f.write(chunk)

examples/historical_batch_list_files.py

@@ -0,0 +1,16 @@
+from pprint import pprint
+
+import databento as db
+
+
+if __name__ == "__main__":
+    db.log = "debug"  # Optional debug logging
+
+    key = "YOUR_API_KEY"
+    client = db.Historical(key=key)
+
+    response = client.batch.list_files(
+        job_id="YOUR_JOB_ID",  # <-- Discover this from `.list_jobs(...)`
+    )
+
+    pprint(response)