gh-35908: some pep8 fixes in homology/
    
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### 📚 Description

This fixes all pycodestyle warnings except `E226` in the `homology`
folder.

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### ⌛ Dependencies

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URL: #35908
Reported by: Frédéric Chapoton
Reviewer(s): Frédéric Chapoton, Matthias Köppe

Author: Release Manager

src/sage/homology/algebraic_topological_model.py

@@ -33,6 +33,7 @@
 from .chain_homotopy import ChainContraction
 from sage.rings.rational_field import QQ
 
+
 def algebraic_topological_model(K, base_ring=None):
     r"""
     Algebraic topological model for cell complex ``K``
@@ -336,6 +337,7 @@ def algebraic_topological_model(K, base_ring=None):
     phi = ChainContraction(phi_data, pi, iota)
     return phi, M
 
+
 def algebraic_topological_model_delta_complex(K, base_ring=None):
     r"""
     Algebraic topological model for cell complex ``K``
@@ -486,7 +488,7 @@ def conditionally_sparse(m):
         iota_cols = {}
         pi_cols_old = pi_cols
         pi_cols = []
-        phi_old = MatrixSpace(base_ring, rank, old_rank, sparse=(base_ring==QQ)).zero()
+        phi_old = MatrixSpace(base_ring, rank, old_rank, sparse=(base_ring == QQ)).zero()
         phi_old_cols = phi_old.columns()
         phi_old = conditionally_sparse(phi_old)
         to_be_deleted = []
@@ -543,8 +545,8 @@ def conditionally_sparse(m):
                 # The matrices involved have many zero entries. For
                 # such matrices, using sparse matrices is faster over
                 # the rationals, slower over finite fields.
-                phi_old = matrix(base_ring, phi_old_cols, sparse=(base_ring==QQ)).transpose()
-                keep = vector(base_ring, pi_nrows, {i:1 for i in range(pi_nrows)
+                phi_old = matrix(base_ring, phi_old_cols, sparse=(base_ring == QQ)).transpose()
+                keep = vector(base_ring, pi_nrows, {i: 1 for i in range(pi_nrows)
                                                     if i not in to_be_deleted})
                 cols = [v.pairwise_product(keep) for v in pi_cols_old]
                 pi_old = MS_pi_t.matrix(cols).transpose()

src/sage/homology/cell_complex.py

@@ -9,4 +9,4 @@
 import sage.topology.cell_complex
 
 GenericCellComplex = deprecated_function_alias(31925,
-                      sage.topology.cell_complex.GenericCellComplex)
+                                               sage.topology.cell_complex.GenericCellComplex)

src/sage/homology/chain_complex.py

@@ -64,6 +64,7 @@
 from sage.misc.superseded import deprecation
 from sage.rings.fast_arith import prime_range
 from sage.homology.homology_group import HomologyGroup
+from sage.misc.persist import register_unpickle_override
 
 
 def _latex_module(R, m):
@@ -248,7 +249,7 @@ def ChainComplex(data=None, base_ring=None, grading_group=None,
         data_dict = {}
     elif isinstance(data, dict):  # data is dictionary
         data_dict = data
-    else: # data is list/tuple/iterable
+    else:  # data is list/tuple/iterable
         data_matrices = [x for x in data if isinstance(x, Matrix)]
         if degree != 1:
             raise ValueError('degree must be +1 if the data argument is a list or tuple')
@@ -667,8 +668,8 @@ def __init__(self, grading_group, degree_of_differential, base_ring, differentia
             sage: TestSuite(C).run()
         """
         if any(d.base_ring() != base_ring or not d.is_immutable() or
-                   (d.ncols(), d.nrows()) == (0, 0)
-                   for d in differentials.values()):
+               (d.ncols(), d.nrows()) == (0, 0)
+               for d in differentials.values()):
             raise ValueError('invalid differentials')
         if degree_of_differential.parent() is not grading_group:
             raise ValueError('the degree_of_differential.parent() must be grading_group')
@@ -1349,15 +1350,15 @@ def change_ring(X):
         d_out_nullity = d_out.ncols() - d_out_rank
 
         if d_in.is_zero():
-            if generators: #Include the generators of the nullspace
-                return [(HomologyGroup(1, base_ring), self({deg:gen}))
+            if generators:  # Include the generators of the nullspace
+                return [(HomologyGroup(1, base_ring), self({deg: gen}))
                         for gen in d_out.right_kernel().basis()]
             else:
                 return HomologyGroup(d_out_nullity, base_ring)
 
         if generators:
             orders, gens = self._homology_generators_snf(d_in, d_out, d_out_rank)
-            answer = [(HomologyGroup(1, base_ring, [order]), self({deg:gen}))
+            answer = [(HomologyGroup(1, base_ring, [order]), self({deg: gen}))
                       for order, gen in zip(orders, gens)]
         else:
             if base_ring.is_field():
@@ -1552,7 +1553,7 @@ def torsion_list(self, max_prime, min_prime=2):
                 for i in diff_dict:
                     if diff_dict[i] != 0:
                         differences.append(i)
-                answer.append((p,differences))
+                answer.append((p, differences))
         return answer
 
     def _Hom_(self, other, category=None):
@@ -1690,7 +1691,7 @@ def _chomp_repr_(self):
         deprecation(33777, "the CHomP interface is deprecated; hence so is this function")
         deg = self.degree_of_differential()
         if (self.grading_group() != ZZ or
-            (deg != 1 and deg != -1)):
+                (deg != 1 and deg != -1)):
             raise ValueError('CHomP only works on Z-graded chain complexes with '
                              'differential of degree 1 or -1')
         base_ring = self.base_ring()
@@ -1702,7 +1703,7 @@ def _chomp_repr_(self):
             diffs = self._flip_().differential()
 
         if len(diffs) == 0:
-            diffs = {0: matrix(ZZ, 0,0)}
+            diffs = {0: matrix(ZZ, 0, 0)}
 
         maxdim = max(diffs)
         mindim = min(diffs)
@@ -2017,7 +2018,7 @@ def cartesian_product(self, *factors, **kwds):
         diffs = [D.differential() for D in factors]
         keys = reduce(lambda X, d: X.union(d.keys()), diffs, set())
         ret = {k: matrix.block_diagonal([d.get(k, zero) for d in diffs],
-                                         subdivide=subdivide)
+                                        subdivide=subdivide)
                for k in keys}
         return ChainComplex(ret, degree_of_differential=deg_diff,
                             grading_group=self._grading_group)
@@ -2182,32 +2183,32 @@ def scalar(a):
             # Our choice for tensor products will be x # y = x1 * y + x2 * y + ...
 
             # Generate the data for the differential
-            for a,r in deg:
-                for b,s in degD:
+            for a, r in deg:
+                for b, s in degD:
                     rp = d[a].nrows()
                     sp = dD[b].nrows()
                     if a+b not in diff:
                         diff[a+b] = {}
                     mor = diff[a+b]
                     cur = {}
-                    cur[(a+deg_diff,b)] = []
-                    cur[(a,b+deg_diff)] = []
+                    cur[(a+deg_diff, b)] = []
+                    cur[(a, b+deg_diff)] = []
 
                     for i in range(r):
                         for j in range(s):
                             # \partial x_i \otimes y_j
                             vec = [zero]*(rp*s)
-                            for k,val in enumerate(d[a].column(i)):
+                            for k, val in enumerate(d[a].column(i)):
                                 vec[s*k+j] += val
-                            cur[(a+deg_diff,b)].append(vec)
+                            cur[(a+deg_diff, b)].append(vec)
 
                             # (-1)^a x_i \otimes \partial y_j
                             vec = [zero]*(r*sp)
-                            for k,val in enumerate(dD[b].column(j)):
+                            for k, val in enumerate(dD[b].column(j)):
                                 vec[sp*i+k] += scalar(a) * val
-                            cur[(a,b+deg_diff)].append(vec)
+                            cur[(a, b+deg_diff)].append(vec)
 
-                    mor[a,b] = cur
+                    mor[a, b] = cur
 
             # Parse the data into matrices
             to_delete = []
@@ -2250,5 +2251,5 @@ def scalar(a):
 
         return ret
 
-from sage.misc.persist import register_unpickle_override
+
 register_unpickle_override('sage.homology.chain_complex', 'ChainComplex', ChainComplex_class)

src/sage/homology/chain_complex_homspace.py

@@ -86,7 +86,7 @@
 
 """
 
-#*****************************************************************************
+# ****************************************************************************
 # Copyright (C) 2009 D. Benjamin Antieau <[email protected]>
 #
 #  Distributed under the terms of the GNU General Public License (GPL)
@@ -100,7 +100,7 @@
 #
 #                  https://www.gnu.org/licenses/
 #
-#*****************************************************************************
+# ****************************************************************************
 
 import sage.categories.homset
 from sage.homology.chain_complex_morphism import ChainComplexMorphism

src/sage/homology/chain_complex_morphism.py

@@ -35,7 +35,7 @@
         [0 0 0]}
 """
 
-#*****************************************************************************
+# ****************************************************************************
 # Copyright (C) 2009 D. Benjamin Antieau <[email protected]>
 #
 #  Distributed under the terms of the GNU General Public License (GPL)
@@ -49,7 +49,7 @@
 #
 #                  https://www.gnu.org/licenses/
 #
-#*****************************************************************************
+# ****************************************************************************
 
 from sage.matrix.constructor import block_diagonal_matrix, zero_matrix
 from sage.categories.morphism import Morphism
@@ -165,8 +165,8 @@ def __init__(self, matrices, C, D, check=True):
             # Check sizes of matrices.
             for i in matrices:
                 if (matrices[i].nrows() != D.free_module_rank(i) or
-                    matrices[i].ncols() != C.free_module_rank(i)):
-                    raise ValueError('matrix in degree {} is not the right size'.format(i))
+                        matrices[i].ncols() != C.free_module_rank(i)):
+                    raise ValueError(f'matrix in degree {i} is not the right size')
             # Check commutativity.
             for i in degrees:
                 if i - d not in degrees:
@@ -187,7 +187,7 @@ def __init__(self, matrices, C, D, check=True):
             # Use immutable matrices because they're hashable.
             m.set_immutable()
             self._matrix_dictionary[i] = m
-        Morphism.__init__(self, Hom(C,D, ChainComplexes(C.base_ring())))
+        Morphism.__init__(self, Hom(C, D, ChainComplexes(C.base_ring())))
 
     def in_degree(self, n):
         """
@@ -324,7 +324,7 @@ def __neg__(self):
             f[i] = -self._matrix_dictionary[i]
         return ChainComplexMorphism(f, self.domain(), self.codomain())
 
-    def __add__(self,x):
+    def __add__(self, x):
         """
         Return ``self + x``.
 
@@ -431,21 +431,21 @@ def __mul__(self, x):
             sage: g._matrix_dictionary
             {1: [], 2: []}
         """
-        if not isinstance(x,ChainComplexMorphism) or self.domain() != x.codomain():
+        if not isinstance(x, ChainComplexMorphism) or self.domain() != x.codomain():
             try:
                 y = self.domain().base_ring()(x)
             except TypeError:
                 raise TypeError("multiplication is not defined")
             f = dict()
             for i in self._matrix_dictionary:
                 f[i] = self._matrix_dictionary[i] * y
-            return ChainComplexMorphism(f,self.domain(),self.codomain())
-        f = dict()
+            return ChainComplexMorphism(f, self.domain(), self.codomain())
+        f = {}
         for i in self._matrix_dictionary:
             f[i] = self._matrix_dictionary[i]*x.in_degree(i)
-        return ChainComplexMorphism(f,x.domain(),self.codomain())
+        return ChainComplexMorphism(f, x.domain(), self.codomain())
 
-    def __rmul__(self,x):
+    def __rmul__(self, x):
         """
         Return ``x * self`` if ``x`` is an element of the base ring.
 
@@ -465,11 +465,11 @@ def __rmul__(self,x):
         except TypeError:
             raise TypeError("multiplication is not defined")
         f = dict()
-        for i in self._matrix_dictionary.keys():
+        for i in self._matrix_dictionary:
             f[i] = y * self._matrix_dictionary[i]
-        return ChainComplexMorphism(f,self.domain(),self.codomain())
+        return ChainComplexMorphism(f, self.domain(), self.codomain())
 
-    def __sub__(self,x):
+    def __sub__(self, x):
         """
         Return ``self - x``.
 
@@ -498,7 +498,7 @@ def __sub__(self,x):
         """
         return self + (-x)
 
-    def __eq__(self,x):
+    def __eq__(self, x):
         """
         Return ``True`` if and only if ``self == x``.
 
@@ -518,12 +518,12 @@ def __eq__(self,x):
             sage: x == y                                                                # optional - sage.graphs
             True
         """
-        return isinstance(x,ChainComplexMorphism) \
-                and self.codomain() == x.codomain() \
-                and self.domain() == x.domain() \
-                and self._matrix_dictionary == x._matrix_dictionary
+        return isinstance(x, ChainComplexMorphism) \
+            and self.codomain() == x.codomain() \
+            and self.domain() == x.domain() \
+            and self._matrix_dictionary == x._matrix_dictionary
 
-    def is_identity(self):
+    def is_identity(self) -> bool:
         """
         Return ``True`` if this is the identity map.
 
@@ -538,7 +538,7 @@ def is_identity(self):
         """
         return self.to_matrix().is_one()
 
-    def is_surjective(self):
+    def is_surjective(self) -> bool:
         """
         Return ``True`` if this map is surjective.
 

src/sage/homology/chain_homotopy.py

@@ -385,6 +385,7 @@ def _repr_(self):
         s += '\n  and {}'.format('\n  '.join(self._g._repr_().split('\n')))
         return s
 
+
 class ChainContraction(ChainHomotopy):
     r"""
     A chain contraction.

src/sage/homology/chains.py

@@ -10,14 +10,14 @@
 complex.
 """
 
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2016 Volker Braun <[email protected]>
 #
 #  Distributed under the terms of the GNU General Public License (GPL)
 #  as published by the Free Software Foundation; either version 2 of
 #  the License, or (at your option) any later version.
-#                  http://www.gnu.org/licenses/
-#*****************************************************************************
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
 
 
 from sage.combinat.free_module import CombinatorialFreeModule
@@ -672,9 +672,9 @@ def cup_product(self, cochain):
             accumulator = codomain.zero()
             for cell in codomain.indices():
                 for (coeff, left_cell, right_cell) in cx.alexander_whitney(cell, left_deg):
-                        if not coeff:
-                            continue
-                        left = left_chains(left_cell)
-                        right = right_chains(right_cell)
-                        accumulator += codomain(cell) * coeff * self.eval(left) * cochain.eval(right)
+                    if not coeff:
+                        continue
+                    left = left_chains(left_cell)
+                    right = right_chains(right_cell)
+                    accumulator += codomain(cell) * coeff * self.eval(left) * cochain.eval(right)
             return accumulator

src/sage/homology/cubical_complex.py

@@ -10,8 +10,8 @@
 
 Cube = deprecated_function_alias(31925, sage.topology.cubical_complex.Cube)
 CubicalComplex = deprecated_function_alias(31925,
-                  sage.topology.cubical_complex.CubicalComplex)
+                                           sage.topology.cubical_complex.CubicalComplex)
 CubicalComplexExamples = deprecated_function_alias(31925,
-                          sage.topology.cubical_complex.CubicalComplexExamples)
+                                                   sage.topology.cubical_complex.CubicalComplexExamples)
 cubical_complexes = deprecated_function_alias(31925,
-                     sage.topology.cubical_complex.cubical_complexes)
+                                              sage.topology.cubical_complex.cubical_complexes)

src/sage/homology/delta_complex.py

@@ -8,8 +8,8 @@
 import sage.topology.delta_complex
 
 DeltaComplex = deprecated_function_alias(31925,
-                sage.topology.delta_complex.DeltaComplex)
+                                         sage.topology.delta_complex.DeltaComplex)
 DeltaComplexExamples = deprecated_function_alias(31925,
-                        sage.topology.delta_complex.DeltaComplexExamples)
+                                                 sage.topology.delta_complex.DeltaComplexExamples)
 delta_complexes = deprecated_function_alias(31925,
-                   sage.topology.delta_complex.delta_complexes)
+                                            sage.topology.delta_complex.delta_complexes)