Remove Python 2 compatibility code and modernize Python style (#20)

- Remove __div__ and __idiv__ methods (Python 2 old-style division)
- Remove explicit object inheritance from BandMat class
- Replace bare except clauses with except (TypeError, ValueError)
- Convert %-style string formatting to f-strings

https://claude.ai/code/session_017xmjvL47SYtX11EZjQ2uSJ

Co-authored-by: Claude <noreply@anthropic.com>

Author: MattShannon

bandmat/core.pyx

@@ -15,7 +15,7 @@ cimport cython
 cnp.import_array()
 cnp.import_ufunc()
 
-class BandMat(object):
+class BandMat:
     """A memory-efficient representation of a square banded matrix.
 
     An N by N matrix with bandwidth D can be stored efficiently by storing its
@@ -56,8 +56,7 @@ class BandMat(object):
         assert self.data.shape[0] == self.l + self.u + 1
 
     def __repr__(self):
-        return ('BandMat(%r, %r, %r, transposed=%r)' %
-                (self.l, self.u, self.data, self.transposed))
+        return f'BandMat({self.l!r}, {self.u!r}, {self.data!r}, transposed={self.transposed!r})'
 
     @property
     def size(self):
@@ -344,7 +343,7 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         return BandMat(self.l, self.u, self.data * mult,
@@ -365,36 +364,16 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         return BandMat(self.l, self.u, self.data.__floordiv__(mult),
                        transposed=self.transposed)
 
-    def __div__(self, other):
-        """Old-style divides a banded matrix by a scalar.
-
-        When using old-style division (c.f. `from __future__ import division`),
-        the expression `a_bm / mult` where `a_bm` is a BandMat is the
-        equivalent of:
-
-            a_full / mult
-
-        where `a_full` is a square numpy array.
-        """
-        try:
-            mult = float(other)
-        except:
-            return NotImplemented
-
-        return BandMat(self.l, self.u, self.data.__div__(mult),
-                       transposed=self.transposed)
-
     def __truediv__(self, other):
         """Divides a banded matrix by a scalar.
 
-        When using new-style division (c.f. `from __future__ import division`),
-        the expression `a_bm / mult` where `a_bm` is a BandMat is the
+        The expression `a_bm / mult` where `a_bm` is a BandMat is the
         equivalent of:
 
             a_full / mult
@@ -403,7 +382,7 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         return BandMat(self.l, self.u, self.data.__truediv__(mult),
@@ -421,7 +400,7 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         self.data *= mult
@@ -439,36 +418,16 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         self.data.__ifloordiv__(mult)
         return self
 
-    def __idiv__(self, other):
-        """Old-style divides this matrix by a scalar in-place.
-
-        When using old-style division (c.f. `from __future__ import division`),
-        the expression `a_bm /= mult` where `a_bm` is a BandMat is the
-        equivalent of:
-
-            a_full /= mult
-
-        where `a_full` is a square numpy array.
-        """
-        try:
-            mult = float(other)
-        except:
-            return NotImplemented
-
-        self.data.__itruediv__(mult)
-        return self
-
     def __itruediv__(self, other):
         """Divides this matrix by a scalar in-place.
 
-        When using new-style division (c.f. `from __future__ import division`),
-        the expression `a_bm /= mult` where `a_bm` is a BandMat is the
+        The statement `a_bm /= mult` where `a_bm` is a BandMat is the
         equivalent of:
 
             a_full /= mult
@@ -477,7 +436,7 @@ class BandMat(object):
         """
         try:
             mult = float(other)
-        except:
+        except (TypeError, ValueError):
             return NotImplemented
 
         self.data.__itruediv__(mult)

bandmat/linalg.pyx

@@ -76,7 +76,7 @@ def _cholesky_banded(cnp.ndarray[cnp.float64_t, ndim=2] mat,
         v0 = mat[<unsigned long>(0), frame]
         if v0 <= 0.0:
             raise sla.LinAlgError(
-                '%d-th leading minor not positive definite' % (frame + 1)
+                f'{frame + 1}-th leading minor not positive definite'
             )
         iv0 = 1.0 / v0
         siv0 = sqrt(iv0)
@@ -167,7 +167,7 @@ def _solve_triangular_banded(cnp.ndarray[cnp.float64_t, ndim=2] a_rect,
                 denom = a_rect[depth, frame]
         if denom == 0.0:
             raise sla.LinAlgError(
-                'singular matrix: resolution failed at diagonal %d' % frame
+                f'singular matrix: resolution failed at diagonal {frame}'
             )
         x[frame] = diff / denom
 

bandmat/test_linalg.py

@@ -167,8 +167,7 @@ def test__solve_triangular_banded(self, its=100):
             b_arg = b.copy()
             if badFrame is not None:
                 msg = (
-                    'singular matrix: resolution failed at diagonal %d' %
-                    badFrame
+                    f'singular matrix: resolution failed at diagonal {badFrame}'
                 )
                 msgRe = '^' + re.escape(msg) + '$'
                 with self.assertRaisesRegex(la.LinAlgError, msgRe):

bandmat/testhelp.py

@@ -11,24 +11,27 @@
 def assert_allclose(actual, desired, rtol=1e-7, atol=1e-14,
                     msg='items not almost equal'):
     if np.shape(actual) != np.shape(desired):
-        raise AssertionError('%s (wrong shape)\n ACTUAL:  %r\n DESIRED: %r' %
-                             (msg, actual, desired))
+        raise AssertionError(
+            f'{msg} (wrong shape)\n ACTUAL:  {actual!r}\n DESIRED: {desired!r}'
+        )
     if not np.allclose(actual, desired, rtol, atol):
         abs_err = np.abs(actual - desired)
         rel_err = np.abs((actual - desired) / desired)
-        raise AssertionError('%s\n ACTUAL:\n%r\n DESIRED:\n%r\n'
-                             ' ABS ERR: %r (max %s)\n REL ERR: %r (max %s)' %
-                             (msg, actual, desired,
-                              abs_err, np.max(abs_err),
-                              rel_err, np.max(rel_err)))
+        raise AssertionError(
+            f'{msg}\n ACTUAL:\n{actual!r}\n DESIRED:\n{desired!r}\n'
+            f' ABS ERR: {abs_err!r} (max {np.max(abs_err)})\n'
+            f' REL ERR: {rel_err!r} (max {np.max(rel_err)})'
+        )
 
 def assert_allequal(actual, desired, msg='items not equal'):
     if np.shape(actual) != np.shape(desired):
-        raise AssertionError('%s (wrong shape)\n ACTUAL:  %r\n DESIRED: %r' %
-                             (msg, actual, desired))
+        raise AssertionError(
+            f'{msg} (wrong shape)\n ACTUAL:  {actual!r}\n DESIRED: {desired!r}'
+        )
     if not np.all(actual == desired):
-        raise AssertionError('%s\n ACTUAL:\n%r\n DESIRED:\n%r' %
-                             (msg, actual, desired))
+        raise AssertionError(
+            f'{msg}\n ACTUAL:\n{actual!r}\n DESIRED:\n{desired!r}'
+        )
 
 def randomize_extra_entries(l, u, mat_rect):
     """Randomizes the extra entries of a rectangular matrix.