diff --git a/scripts/add_brownfield.py b/scripts/add_brownfield.py
index 0f3cb318c..c1be48968 100644
--- a/scripts/add_brownfield.py
+++ b/scripts/add_brownfield.py
@@ -242,12 +242,17 @@ def update_heat_pump_efficiency(n: pypsa.Network, n_p: pypsa.Network, year: int)
     """
 
     # get names of heat pumps in previous iteration
-    heat_pump_idx_previous_iteration = n_p.links.index[n_p.links.index.str.contains("heat pump")]
+    heat_pump_idx_previous_iteration = n_p.links.index[
+        n_p.links.index.str.contains("heat pump")
+    ]
     # construct names of same-technology heat pumps in the current iteration
-    corresponding_idx_this_iteration = heat_pump_idx_previous_iteration.str[:-4] + str(year)  
+    corresponding_idx_this_iteration = heat_pump_idx_previous_iteration.str[:-4] + str(
+        year
+    )
     # update efficiency of heat pumps in previous iteration in-place to efficiency in this iteration
-    n_p.links_t["efficiency"].loc[:, heat_pump_idx_previous_iteration] = n.links_t["efficiency"].loc[:, corresponding_idx_this_iteration].values
-
+    n_p.links_t["efficiency"].loc[:, heat_pump_idx_previous_iteration] = (
+        n.links_t["efficiency"].loc[:, corresponding_idx_this_iteration].values
+    )
 
 
 if __name__ == "__main__":
diff --git a/scripts/prepare_perfect_foresight.py b/scripts/prepare_perfect_foresight.py
index 50992d4c6..53895d0a2 100644
--- a/scripts/prepare_perfect_foresight.py
+++ b/scripts/prepare_perfect_foresight.py
@@ -521,9 +521,6 @@ def update_heat_pump_efficiency(n: pypsa.Network, years: List[int]):
         ] = correct_efficiency.values
 
 
-
-
-
 if __name__ == "__main__":
     if "snakemake" not in globals():
         from _helpers import mock_snakemake