Replace [column] access with .loc[:, column]

At least in the places where I noticed.
This makes it easier to see, whether the indexing is done into a
dictionary, `Series` or list, i.e. a normally one dimensional structure,
or a `DataFrame`, which is always two dimensional.

src/egon/data/datasets/pypsaeursec/__init__.py

@@ -555,7 +555,7 @@ def neighbor_reduction():
     engine = db.engine()
 
     neighbors.loc[:, "scn_name"] = "eGon100RE"
-    neighbors.index = neighbors["new_index"]
+    neighbors.index = neighbors.loc[:, "new_index"]
 
     # Correct geometry for non AC buses
     carriers = set(neighbors.carrier.to_list())
@@ -610,10 +610,10 @@ def neighbor_reduction():
     # prepare and write neighboring crossborder lines to etrago tables
     def lines_to_etrago(neighbor_lines=neighbor_lines, scn="eGon100RE"):
         neighbor_lines.loc[:, "scn_name"] = scn
-        neighbor_lines.loc[:, "cables"] = 3 * neighbor_lines[
-            "num_parallel"
+        neighbor_lines.loc[:, "cables"] = 3 * neighbor_lines.loc[
+            :, "num_parallel"
         ].astype(int)
-        neighbor_lines.loc[:, "s_nom"] = neighbor_lines["s_nom_min"]
+        neighbor_lines.loc[:, "s_nom"] = neighbor_lines.loc[:, "s_nom_min"]
 
         for i in [
             "name",
@@ -809,7 +809,7 @@ def links_to_etrago(neighbor_links, scn="eGon100RE", extendable=True):
 
     # prepare neighboring generators for etrago tables
     neighbor_gens.loc[:, "scn_name"] = "eGon100RE"
-    neighbor_gens.loc[:, "p_nom"] = neighbor_gens["p_nom_opt"]
+    neighbor_gens.loc[:, "p_nom"] = neighbor_gens.loc[:, "p_nom_opt"]
     neighbor_gens.loc[:, "p_nom_extendable"] = False
 
     # Unify carrier names