diff --git a/bin/xtgls.py b/bin/xtgls.py
index 4b53e06fc..5b9c019a6 100644
--- a/bin/xtgls.py
+++ b/bin/xtgls.py
@@ -1,4 +1,5 @@
 """xtgls: a small script for listing xtg formatted files."""
+
 import argparse
 import json
 import pathlib
diff --git a/examples/grid3d_prop_as_map.py b/examples/grid3d_prop_as_map.py
index e2a800500..08e5a3ab8 100644
--- a/examples/grid3d_prop_as_map.py
+++ b/examples/grid3d_prop_as_map.py
@@ -2,6 +2,7 @@
 Make a regularmap from a property at a given K layer
 By JRIV
 """
+
 import os
 
 import xtgeo
diff --git a/examples/surface_slice_grid3d.py b/examples/surface_slice_grid3d.py
index 6b276a7b0..3cdc544f6 100644
--- a/examples/surface_slice_grid3d.py
+++ b/examples/surface_slice_grid3d.py
@@ -7,6 +7,7 @@
 
 JRIV
 """
+
 import os
 import pathlib
 import tempfile
diff --git a/src/xtgeo/grid3d/_grdecl_grid.py b/src/xtgeo/grid3d/_grdecl_grid.py
index 0cd889963..3d2c74759 100644
--- a/src/xtgeo/grid3d/_grdecl_grid.py
+++ b/src/xtgeo/grid3d/_grdecl_grid.py
@@ -20,6 +20,7 @@
 of how these keywords are layed out in a text file, and see GrdeclGrid
 for how the grid geometry is interpreted from these keywords.
 """
+
 from __future__ import annotations
 
 from dataclasses import dataclass
diff --git a/src/xtgeo/grid3d/_grid3d_fence.py b/src/xtgeo/grid3d/_grid3d_fence.py
index 79db6ee00..0b534a893 100644
--- a/src/xtgeo/grid3d/_grid3d_fence.py
+++ b/src/xtgeo/grid3d/_grid3d_fence.py
@@ -1,4 +1,5 @@
 """Some grid utilities, file scanning etc."""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING
diff --git a/src/xtgeo/grid3d/_grid_import_ecl.py b/src/xtgeo/grid3d/_grid_import_ecl.py
index a6cdd623b..5b3f41309 100644
--- a/src/xtgeo/grid3d/_grid_import_ecl.py
+++ b/src/xtgeo/grid3d/_grid_import_ecl.py
@@ -1,4 +1,5 @@
 """Grid import functions for Eclipse, new approach (i.e. version 2)."""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Any
diff --git a/src/xtgeo/grid3d/_grid_import_roff.py b/src/xtgeo/grid3d/_grid_import_roff.py
index 755ad213f..c951a4d44 100644
--- a/src/xtgeo/grid3d/_grid_import_roff.py
+++ b/src/xtgeo/grid3d/_grid_import_roff.py
@@ -1,4 +1,5 @@
 """Private module, Grid Import private functions for ROFF format."""
+
 from __future__ import annotations
 
 import pathlib
diff --git a/src/xtgeo/grid3d/_grid_import_xtgcpgeom.py b/src/xtgeo/grid3d/_grid_import_xtgcpgeom.py
index 75feb3b1e..50662242c 100644
--- a/src/xtgeo/grid3d/_grid_import_xtgcpgeom.py
+++ b/src/xtgeo/grid3d/_grid_import_xtgcpgeom.py
@@ -1,4 +1,5 @@
 """Private module, Grid Import private functions for xtgeo based formats."""
+
 from __future__ import annotations
 
 import json
@@ -52,13 +53,11 @@ class _META(TypedDict):
 
 
 @overload
-def convert_subgrids(sdict: dict[str, int]) -> dict[str, range]:
-    ...
+def convert_subgrids(sdict: dict[str, int]) -> dict[str, range]: ...
 
 
 @overload
-def convert_subgrids(sdict: None) -> None:
-    ...
+def convert_subgrids(sdict: None) -> None: ...
 
 
 def convert_subgrids(sdict: dict[str, int] | None) -> dict[str, range] | None:
diff --git a/src/xtgeo/grid3d/_grid_refine.py b/src/xtgeo/grid3d/_grid_refine.py
index 773db9cb5..63ea91d87 100644
--- a/src/xtgeo/grid3d/_grid_refine.py
+++ b/src/xtgeo/grid3d/_grid_refine.py
@@ -1,4 +1,5 @@
 """Private module for refinement of a grid."""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING
diff --git a/src/xtgeo/grid3d/_grid_wellzone.py b/src/xtgeo/grid3d/_grid_wellzone.py
index 13061c29d..1a7748d35 100644
--- a/src/xtgeo/grid3d/_grid_wellzone.py
+++ b/src/xtgeo/grid3d/_grid_wellzone.py
@@ -1,4 +1,5 @@
 """Private module for grid vs well zonelog checks."""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Literal
diff --git a/src/xtgeo/grid3d/_gridprop_import_grdecl.py b/src/xtgeo/grid3d/_gridprop_import_grdecl.py
index 5430d74f8..6ba5ade56 100644
--- a/src/xtgeo/grid3d/_gridprop_import_grdecl.py
+++ b/src/xtgeo/grid3d/_gridprop_import_grdecl.py
@@ -1,4 +1,5 @@
 """Importing grid props from GRDECL, ascii or binary"""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Any
diff --git a/src/xtgeo/grid3d/_gridprop_lowlevel.py b/src/xtgeo/grid3d/_gridprop_lowlevel.py
index 65758a574..c2d79605d 100644
--- a/src/xtgeo/grid3d/_gridprop_lowlevel.py
+++ b/src/xtgeo/grid3d/_gridprop_lowlevel.py
@@ -1,4 +1,5 @@
 """GridProperty (not GridProperies) low level functions"""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Literal
diff --git a/src/xtgeo/grid3d/_gridprop_op1.py b/src/xtgeo/grid3d/_gridprop_op1.py
index aaecf8a49..ca5dc4b3a 100644
--- a/src/xtgeo/grid3d/_gridprop_op1.py
+++ b/src/xtgeo/grid3d/_gridprop_op1.py
@@ -1,4 +1,5 @@
 """Various grid property operations"""
+
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, List, Literal, Optional, Tuple, Union
diff --git a/src/xtgeo/grid3d/_gridprop_roxapi.py b/src/xtgeo/grid3d/_gridprop_roxapi.py
index 05b9e2c73..466668c3a 100644
--- a/src/xtgeo/grid3d/_gridprop_roxapi.py
+++ b/src/xtgeo/grid3d/_gridprop_roxapi.py
@@ -1,5 +1,6 @@
 # coding: utf-8
 """Roxar API functions for XTGeo Grid Property."""
+
 from __future__ import annotations
 
 import contextlib
diff --git a/src/xtgeo/surface/_regsurf_roxapi.py b/src/xtgeo/surface/_regsurf_roxapi.py
index 97c5abbc5..ad952439c 100644
--- a/src/xtgeo/surface/_regsurf_roxapi.py
+++ b/src/xtgeo/surface/_regsurf_roxapi.py
@@ -1,5 +1,6 @@
 # coding: utf-8
 """Roxar API functions for XTGeo RegularSurface."""
+
 import os
 import tempfile
 
diff --git a/src/xtgeo/surface/regular_surface.py b/src/xtgeo/surface/regular_surface.py
index 448bd6c3e..2b7ebe223 100644
--- a/src/xtgeo/surface/regular_surface.py
+++ b/src/xtgeo/surface/regular_surface.py
@@ -32,7 +32,6 @@
 # For functions with mask=... ,the should be replaced with asmasked=...
 # --------------------------------------------------------------------------------------
 
-
 from __future__ import annotations
 
 import functools
diff --git a/src/xtgeo/xyz/__init__.py b/src/xtgeo/xyz/__init__.py
index a0c543f4e..b5d8ad4d4 100644
--- a/src/xtgeo/xyz/__init__.py
+++ b/src/xtgeo/xyz/__init__.py
@@ -1,6 +1,5 @@
 """The XTGeo xyz (points and polygons) package."""
 
-
 # flake8: noqa
 from xtgeo.xyz._xyz import XYZ
 from xtgeo.xyz.points import Points
diff --git a/src/xtgeo/xyz/_xyz_oper.py b/src/xtgeo/xyz/_xyz_oper.py
index aa35fee5b..31d93de16 100644
--- a/src/xtgeo/xyz/_xyz_oper.py
+++ b/src/xtgeo/xyz/_xyz_oper.py
@@ -1,7 +1,6 @@
 # coding: utf-8
 """Various operations on XYZ data"""
 
-
 import numpy as np
 import pandas as pd
 import shapely.geometry as sg
diff --git a/src/xtgeo/xyz/_xyz_roxapi.py b/src/xtgeo/xyz/_xyz_roxapi.py
index 5e142d7c1..35d487899 100644
--- a/src/xtgeo/xyz/_xyz_roxapi.py
+++ b/src/xtgeo/xyz/_xyz_roxapi.py
@@ -1,5 +1,6 @@
 # coding: utf-8
 """Roxar API functions for XTGeo Points/Polygons"""
+
 from __future__ import annotations
 
 import os
diff --git a/tests/test_grid3d/test_grid_property_etc.py b/tests/test_grid3d/test_grid_property_etc.py
index e8d006620..9437cb009 100644
--- a/tests/test_grid3d/test_grid_property_etc.py
+++ b/tests/test_grid3d/test_grid_property_etc.py
@@ -1,5 +1,6 @@
 # coding: utf-8
 """Testing: test_grid_property more special functions"""
+
 import pytest
 from xtgeo.grid3d import _gridprop_roxapi
 
diff --git a/tests/test_grid3d/test_grid_property_roff.py b/tests/test_grid3d/test_grid_property_roff.py
index d259e2308..b777a6e76 100644
--- a/tests/test_grid3d/test_grid_property_roff.py
+++ b/tests/test_grid3d/test_grid_property_roff.py
@@ -152,7 +152,7 @@ def test_xtgeo_codes(param, expected_codes):
 
 
 def test_to_file(tmp_path):
-    roff_param = RoffParameter(1, 1, 2, "", b"\x01\xFF")
+    roff_param = RoffParameter(1, 1, 2, "", b"\x01\xff")
     roff_param.to_file(tmp_path / "param.roff")
     vals = roffio.read(tmp_path / "param.roff")
     assert vals["parameter"] == {"name": "", "data": b"\x01\xff"}
@@ -166,7 +166,7 @@ def test_to_file_codes():
         1,
         2,
         "a",
-        b"\x01\xFF",
+        b"\x01\xff",
         code_names=["a", "b"],
         code_values=np.array([1, 2], dtype=np.int32),
     )
diff --git a/tests/test_grid3d/test_grid_xtgformats_io.py b/tests/test_grid3d/test_grid_xtgformats_io.py
index 0effd45eb..af5cc3855 100644
--- a/tests/test_grid3d/test_grid_xtgformats_io.py
+++ b/tests/test_grid3d/test_grid_xtgformats_io.py
@@ -1,5 +1,6 @@
 # coding: utf-8
 """Testing new xtgf and hdf5/h5 formats."""
+
 from os.path import join
 
 import hypothesis.strategies as st