removed unused variable, and converted to f-string

Signed-off-by: Nick Papior <[email protected]>

src/sisl/geom/_common.py

@@ -10,7 +10,7 @@ def geometry_define_nsc(geometry, periodic=(True, True, True)):
     """Define the number of supercells for a geometry based on the periodicity """
     if np.all(geometry.maxR(True) > 0.):
         geometry.optimize_nsc()
-        for i, d, per in zip(range(3), "abc", periodic):
+        for d, per in zip("abc", periodic):
             if per:
                 geometry.lattice.set_boundary_condition(**{d: "Periodic"})
             else:

src/sisl/geometry.py

@@ -1692,7 +1692,7 @@ def optimize_nsc(self, axis=None, R=None) -> ndarray:
             R = self.maxR() + 0.001
         if R < 0:
             R = 0.00001
-            warn(self.__class__.__name__ +
+            warn(f"{self.__class__.__name__}"
                  ".optimize_nsc could not determine the radius from the "
                  "internal atoms (defaulting to zero radius).")