diff --git a/etrago/cluster/snapshot.py b/etrago/cluster/snapshot.py
index fbbd1f68..8afec2f1 100644
--- a/etrago/cluster/snapshot.py
+++ b/etrago/cluster/snapshot.py
@@ -26,9 +26,10 @@
 ( https://github.com/FZJ-IEK3-VSA/tsam ) developed by Leander Kotzur et al.
 """
 
-import pandas as pd
 import os
 
+import pandas as pd
+
 if "READTHEDOCS" not in os.environ:
     import pyomo.environ as po
     import tsam.timeseriesaggregation as tsam
diff --git a/etrago/tools/calc_results.py b/etrago/tools/calc_results.py
index f3e3338d..aa6c6cb2 100755
--- a/etrago/tools/calc_results.py
+++ b/etrago/tools/calc_results.py
@@ -24,11 +24,11 @@
 import os
 
 if "READTHEDOCS" not in os.environ:
-    import time
     import logging
+    import time
 
-    import pandas as pd
     import numpy as np
+    import pandas as pd
 
     logger = logging.getLogger(__name__)
 
diff --git a/etrago/tools/extendable.py b/etrago/tools/extendable.py
index 6bb56658..ba4be517 100644
--- a/etrago/tools/extendable.py
+++ b/etrago/tools/extendable.py
@@ -21,16 +21,14 @@
 """
 Extendable.py defines function to set PyPSA components extendable.
 """
-from etrago.tools.utilities import convert_capital_costs, find_snapshots
-
-from etrago.cluster.snapshot import snapshot_clustering
+from math import sqrt
+import time
 
 import numpy as np
 import pandas as pd
 
-import time
-from math import sqrt
-
+from etrago.cluster.snapshot import snapshot_clustering
+from etrago.tools.utilities import convert_capital_costs, find_snapshots
 
 __copyright__ = (
     "Flensburg University of Applied Sciences, "
diff --git a/etrago/tools/plot.py b/etrago/tools/plot.py
index d3ae2068..cc290c63 100644
--- a/etrago/tools/plot.py
+++ b/etrago/tools/plot.py
@@ -45,9 +45,9 @@
 
 if "READTHEDOCS" not in os.environ:
     from geoalchemy2.shape import to_shape
-    import geopandas as gpd
     from pyproj import Proj, transform
     from shapely.geometry import LineString, MultiPoint, Point, Polygon
+    import geopandas as gpd
     import tilemapbase
 
 __copyright__ = (