gh-35931: cython-lint: full fix in cpython/ probability/ media/ and sat/ folders
    
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fixing some cython-lint suggestions in a few folders, mostly in
`cpython`

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URL: #35931
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/cpython/atexit.pyx

@@ -2,15 +2,15 @@
 
 """Utilities for interfacing with the standard library's atexit module."""
 
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2017 Erik M. Bray <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License 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/
+# ****************************************************************************
 
 import atexit
 
@@ -51,7 +51,8 @@ cdef class restore_atexit:
         sage: import atexit
         sage: from sage.cpython.atexit import restore_atexit
         sage: def handler(*args, **kwargs):
-        ....:     import sys # see https://github.com/sagemath/sage/issues/25270#comment:56
+        ....:     import sys
+        ....:     # see https://github.com/sagemath/sage/issues/25270#comment:56
         ....:     sys.stdout.write(str((args, kwargs)))
         ....:     sys.stdout.write('\n')
         sage: atexit.register(handler, 1, 2, c=3)
@@ -188,6 +189,7 @@ cdef extern from *:
         PyObject* kwargs
     atexit_callback** _atexit_callbacks(object module)
 
+
 def _get_exithandlers():
     """Return list of exit handlers registered with the atexit module."""
     cdef atexit_callback ** callbacks
@@ -206,10 +208,11 @@ def _get_exithandlers():
         else:
             kwargs = {}
         exithandlers.append((<object>callback.func,
-                                <object>callback.args,
-                                kwargs))
+                             <object>callback.args,
+                             kwargs))
     return exithandlers
 
+
 def _set_exithandlers(exithandlers):
     """
     Replace the list of exit handlers registered with the atexit module

src/sage/cpython/debug.pyx

@@ -1,19 +1,18 @@
 """
 Various functions to debug Python internals
 """
-
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2017 Jeroen Demeyer <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License 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 cpython.object cimport (PyObject, PyTypeObject, Py_TYPE,
-        descrgetfunc, descrsetfunc)
+                             descrgetfunc, descrsetfunc)
 
 cdef extern from "Python.h":
     # Helper to get a pointer to an object's __dict__ slot, if any
@@ -58,6 +57,7 @@ def shortrepr(obj, max=50):
 
 cdef object _no_default = object()  # Unique object
 
+
 def getattr_debug(obj, name, default=_no_default):
     r"""
     A re-implementation of ``getattr()`` with lots of debugging info.
@@ -153,9 +153,9 @@ def getattr_debug(obj, name, default=_no_default):
             dct = <object>(dictptr[0])
             print(f"  object has __dict__ slot ({type(dct)})")
         else:
-            print(f"  object has uninitialized __dict__ slot")
+            print("  object has uninitialized __dict__ slot")
     else:
-        print(f"  object does not have __dict__ slot")
+        print("  object does not have __dict__ slot")
 
     cdef descrgetfunc get = NULL
     cdef descrsetfunc set = NULL
@@ -172,15 +172,15 @@ def getattr_debug(obj, name, default=_no_default):
             set = Py_TYPE(attr).tp_descr_set
             if get is not NULL:
                 if set is not NULL:
-                    print(f"  attribute is data descriptor (has __get__ and __set__)")
+                    print("  attribute is data descriptor (has __get__ and __set__)")
                     if dct is not None:
-                        print(f"  ignoring __dict__ because we have a data descriptor")
-                    print(f"  calling __get__()")
+                        print("  ignoring __dict__ because we have a data descriptor")
+                    print("  calling __get__()")
                     attr = get(attr, obj, type(obj))
                     print(f"  returning {shortrepr(attr)} ({type(attr)})")
                     return attr
                 else:
-                    print(f"  attribute is ordinary descriptor (has __get__)")
+                    print("  attribute is ordinary descriptor (has __get__)")
             attr_in_class = True
             break
 
@@ -198,22 +198,22 @@ def getattr_debug(obj, name, default=_no_default):
 
     if attr_in_class:
         if get is not NULL:
-            print(f"  calling __get__()")
+            print("  calling __get__()")
             attr = get(attr, obj, type(obj))
         print(f"  returning {shortrepr(attr)} ({type(attr)})")
         return attr
 
     try:
         tpgetattr = type(obj).__getattr__
     except AttributeError:
-        print(f"  class does not have __getattr__")
+        print("  class does not have __getattr__")
     else:
-        print(f"  calling __getattr__()")
+        print("  calling __getattr__()")
         attr = tpgetattr(obj, name)
         print(f"  returning {shortrepr(attr)} ({type(attr)})")
         return attr
 
-    print(f"  attribute not found")
+    print("  attribute not found")
     raise AttributeError(AttributeErrorMessage(obj, name))
 
 

src/sage/cpython/dict_del_by_value.pyx

@@ -160,12 +160,13 @@ cdef int del_dictitem_by_exact_value(PyDictObject *mp, PyObject *value, Py_hash_
     ep.me_value = NULL
     mp.ma_used -= 1
     dictkeys_set_index(keys, i, DKIX_DUMMY)
-    #We have transferred the to-be-deleted references to the list T
-    #we now delete the list so that the actual decref happens through a
-    #deallocation routine that uses the Python Trashcan macros to
-    #avoid stack overflow in deleting deep structures.
+    # We have transferred the to-be-deleted references to the list T
+    # we now delete the list so that the actual decref happens through a
+    # deallocation routine that uses the Python Trashcan macros to
+    # avoid stack overflow in deleting deep structures.
     del T
 
+
 def test_del_dictitem_by_exact_value(D, value, h):
     """
     This function helps testing some cdef function used to delete dictionary items.

src/sage/cpython/string.pxd

@@ -1,14 +1,12 @@
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2017 Erik M. Bray <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License 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/
+# ****************************************************************************
 
 cdef extern from "string_impl.h":
     str _cstr_to_str(const char* c, encoding, errors)

src/sage/cpython/string.pyx

@@ -14,15 +14,15 @@ Check that this can be used outside of Sage (see :trac:`25549`)::
     hello world!
 """
 
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2017 Erik M. Bray <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License 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/
+# ****************************************************************************
 
 import sys
 

src/sage/cpython/wrapperdescr.pyx

@@ -97,6 +97,6 @@ cdef wrapperdescr_fastcall(wrapper_descriptor slotwrapper, self, args, kwds):
 
     if <PyObject*>kwds is not NULL and kwds:
         raise TypeError(f"wrapper {bytes_to_str(slotdef.name)} slotdef "
-                         "doesn't take keyword arguments")
+                        "doesn't take keyword arguments")
 
     return slotdef.wrapper(self, args, slotwrapper.d_wrapped)

src/sage/media/channels.pyx

@@ -1,8 +1,9 @@
 "_separate_channels"
 
+
 def _separate_channels(_data, _width, _nchannels):
     """
-    Separates the channels. This is an internal helper method for
+    Separate the channels. This is an internal helper method for
     precomputing some data while initializing the wav object.
     """
     cdef int nchannels = _nchannels
@@ -11,21 +12,21 @@ def _separate_channels(_data, _width, _nchannels):
     cdef int n
     cdef short int x
 
-    cdef int l = len(_data) / (width)
+    cdef int ell = len(_data) // width
 
     channel_data = [[] for i in range(nchannels)]
     if width == 1:
         # handle the one byte case
 
-        for n in range(l):
-            channel_data[n % nchannels].append(ord(data[n])-127)
+        for n in range(ell):
+            channel_data[n % nchannels].append(ord(data[n]) - 127)
 
     elif width == 2:
-        a = 32768
-        for n in range(l):
+        # a = 32768
+        for n in range(ell):
             # compute the value as an integer
-            x = <int> (data[2*n]) + 256 * <int>(data[2*n + 1])
-            #x -= 65536*(x > a)
+            x = <int> (data[2*n]) + 256 * <int>(data[2 * n + 1])
+            # x -= 65536*(x > a)
             channel_data[n % nchannels].append(x)
     else:
         raise NotImplementedError("greater than 16-bit wavs not supported")

src/sage/probability/probability_distribution.pyx

@@ -140,8 +140,8 @@ cdef class ProbabilityDistribution:
              2.0]
         """
         import pylab
-        l = [float(self.get_random_element()) for _ in range(num_samples)]
-        S = pylab.hist(l, bins, density=True)
+        ell = [float(self.get_random_element()) for _ in range(num_samples)]
+        S = pylab.hist(ell, bins, density=True)
         return [list(S[0]), list(S[1])]
 
     def generate_histogram_plot(self, name, num_samples = 1000, bins = 50):
@@ -171,8 +171,8 @@ cdef class ProbabilityDistribution:
             ....:     X.generate_histogram_plot(f.name)
         """
         import pylab
-        l = [float(self.get_random_element()) for _ in range(num_samples)]
-        pylab.hist(l, bins, density=True)
+        ell = [float(self.get_random_element()) for _ in range(num_samples)]
+        pylab.hist(ell, bins, density=True)
         pylab.savefig(name)
 
 
@@ -309,7 +309,7 @@ cdef class SphericalDistribution(ProbabilityDistribution):
         gsl_ran_dir_nd(self.r, self.dimension, self.vec)
         for i in range(self.dimension):
             v[i] = self.vec[i]
-        return vector(sage.rings.real_double.RDF, v) #This could be made more efficient by directly constructing the vector, TODO.
+        return vector(sage.rings.real_double.RDF, v)  # This could be made more efficient by directly constructing the vector, TODO.
 
     def reset_distribution(self):
         """
@@ -542,11 +542,12 @@ cdef class RealDistribution(ProbabilityDistribution):
     cdef double* parameters
     cdef long int seed
     cdef object name
-    #cdef double (*generator_1)(gsl_rng*)
-    #cdef double (*generator_2)(gsl_rng*, double)
-    #cdef _get_random_element_c(self)
+    # cdef double (*generator_1)(gsl_rng*)
+    # cdef double (*generator_2)(gsl_rng*, double)
+    # cdef _get_random_element_c(self)
 
-    def __init__(self, type = 'uniform', parameters = [], rng = 'default', seed = None):
+    def __init__(self, type='uniform', parameters=None,
+                 rng='default', seed=None):
         r"""
         EXAMPLES::
 
@@ -571,7 +572,6 @@ cdef class RealDistribution(ProbabilityDistribution):
             sage: one == three
             False
         """
-
         gsl_rng_env_setup()
         self.parameters = NULL
         self.set_random_number_generator(rng)
@@ -681,7 +681,7 @@ cdef class RealDistribution(ProbabilityDistribution):
 
         return sage.rings.real_double.RDF(result)
 
-    def set_distribution(self, name = 'uniform', parameters = []):
+    def set_distribution(self, name='uniform', parameters=None):
         """
         This method can be called to change the current probability distribution.
 
@@ -693,6 +693,9 @@ cdef class RealDistribution(ProbabilityDistribution):
         """
         sig_free(self.parameters)
 
+        if parameters is None:
+            parameters = []
+
         if name == 'uniform':
             self.distribution_type = uniform
             for x in parameters:
@@ -809,7 +812,7 @@ cdef class RealDistribution(ProbabilityDistribution):
 
         self.name = name
 
-    #def _get_random_element_c():
+    # def _get_random_element_c():
 
     def reset_distribution(self):
         """
@@ -1028,7 +1031,6 @@ cdef class GeneralDiscreteDistribution(ProbabilityDistribution):
         ...
         ValueError: The distribution probabilities must be non-negative
     """
-
     cdef gsl_rng_type * T
     cdef gsl_rng * r
     cdef gsl_ran_discrete_t *dist
@@ -1070,7 +1072,6 @@ cdef class GeneralDiscreteDistribution(ProbabilityDistribution):
             sage: X = GeneralDiscreteDistribution([1,2,2^1024])
             sage: Counter(X.get_random_element() for _ in range(100))
             Counter({2: 100})
-
         """
         gsl_rng_env_setup()
         self.set_random_number_generator(rng)
@@ -1093,7 +1094,7 @@ cdef class GeneralDiscreteDistribution(ProbabilityDistribution):
         for i in range(n):
             if P[i] < 0:
                 raise ValueError("The distribution probabilities must "
-                    "be non-negative")
+                                 "be non-negative")
             P_vec[i] = P[i]
 
         self.dist = gsl_ran_discrete_preproc(n, P_vec)
@@ -1111,7 +1112,6 @@ cdef class GeneralDiscreteDistribution(ProbabilityDistribution):
             sage: X.get_random_element()
             1
         """
-
         gsl_rng_set(self.r, seed)
         self.seed = seed
 
@@ -1124,7 +1124,6 @@ cdef class GeneralDiscreteDistribution(ProbabilityDistribution):
             sage: X = GeneralDiscreteDistribution([0.3, 0.4, 0.3])
             sage: X.set_random_number_generator('taus')
         """
-
         if rng == 'default':
             self.T = gsl_rng_default
         elif rng == 'luxury':

src/sage/sat/solvers/satsolver.pyx

@@ -158,7 +158,7 @@ cdef class SatSolver:
             if line.startswith("x"):
                 line = line[1:].split(" ")
                 clause = [int(e) for e in line if e]
-                clause = clause[:-1] # strip trailing zero
+                clause = clause[:-1]  # strip trailing zero
                 try:
                     self.add_xor_clause(clause)
                 except AttributeError: