DOI-USGS · thodson-usgs · May 3, 2026 · May 4, 2026 · May 4, 2026 · May 5, 2026
diff --git a/dataretrieval/utils.py b/dataretrieval/utils.py
@@ -163,7 +163,7 @@ def query(url, payload, delimiter=",", ssl_check=True):
     url: string
         URL to query
     payload: dict
-        query parameters passed to ``requests.get``
+        query parameters passed to ``requests.get``. Not mutated.
     delimiter: string
         delimiter to use with lists
     ssl_check: bool
@@ -172,20 +172,23 @@ def query(url, payload, delimiter=",", ssl_check=True):
 
     Returns
     -------
-    string: query response
-        The response from the API query ``requests.get`` function call.
+    response : ``requests.Response``
+        The response object from the underlying ``requests.get`` call.
+
+    Raises
+    ------
+    ValueError
+        For any non-success HTTP status (4xx/5xx). The message includes
+        the status code, reason, and URL. Specific guidance is included
+        for 400, 404, 414, and 500/502/503 statuses; any other 4xx/5xx
+        falls through to a generic ValueError so callers don't silently
+        receive an HTML error page as if it were data.
     """
+    params = {key: to_str(value, delimiter) for key, value in payload.items()}
 
-    for key, value in payload.items():
-        payload[key] = to_str(value, delimiter)
-    # for index in range(len(payload)):
-    #    key, value = payload[index]
-    #    payload[index] = (key, to_str(value))
-
-    # define the user agent for the query
     user_agent = {"user-agent": f"python-dataretrieval/{dataretrieval.__version__}"}
 
-    response = requests.get(url, params=payload, headers=user_agent, verify=ssl_check)
+    response = requests.get(url, params=params, headers=user_agent, verify=ssl_check)
 
     if response.status_code == 400:
         raise ValueError(
@@ -218,6 +221,15 @@ def query(url, payload, delimiter=",", ssl_check=True):
             + f"The service at {response.url} may be down or experiencing issues."
         )
 
+    # Catch-all for any other 4xx/5xx (401, 403, 405, 408, 429, 501, 504, ...)
+    # so callers don't silently receive an HTML error page as if it were data.
+    # Re-raise as ValueError to keep the exception contract uniform with the
+    # explicit status branches above.
+    if not response.ok:
+        raise ValueError(
+            f"HTTP {response.status_code} {response.reason} for {response.url}"
+        )
+
     if response.text.startswith("No sites/data"):
         raise NoSitesError(response.url)
 

diff --git a/tests/utils_test.py b/tests/utils_test.py
@@ -41,6 +41,37 @@ def test_header(self):
         assert response.status_code == 200  # GET was successful
         assert "user-agent" in response.request.headers
 
+    def test_does_not_mutate_caller_payload(self, requests_mock):
+        """`query` must not mutate the caller's payload dict.
+
+        Regression: previously the function did
+        ``payload[key] = to_str(value, delimiter)`` in place, so list
+        values were overwritten with their stringified joins after the
+        call returned.
+        """
+        url = "https://example.com/svc"
+        requests_mock.get(url, text="ok")
+        payload = {"sites": ["A", "B"], "stateCd": "MD"}
+        original = {k: v for k, v in payload.items()}
+
+        utils.query(url, payload)
+
+        assert payload == original
+        assert payload["sites"] is original["sites"]
+
+    @pytest.mark.parametrize("status", [401, 403, 405, 408, 429, 501, 504])
+    def test_unhandled_4xx_5xx_raises(self, requests_mock, status):
+        """`query` must surface every 4xx/5xx, not just the few it formats.
+
+        Regression: codes outside {400, 404, 414, 500, 502, 503} used to
+        pass through silently — callers received the error body as if
+        it were data.
+        """
+        url = "https://example.com/svc"
+        requests_mock.get(url, status_code=status, text="<html>denied</html>")
+        with pytest.raises(ValueError, match=str(status)):
+            utils.query(url, {"k": "v"})
+
 
 class Test_BaseMetadata:
     """Tests of BaseMetadata"""