using pathlib in 3 files

src/sage/rings/polynomial/pbori/nf.py

@@ -1,3 +1,6 @@
+from pathlib import Path
+from warnings import warn
+
 from sage.rings.polynomial.pbori.pbori import mod_mon_set
 from .pbori import (BooleSet, GroebnerStrategy, ReductionStrategy,
                     parallel_reduce, easy_linear_factors)
@@ -6,8 +9,6 @@
 from .easy_polynomials import (easy_linear_polynomials as
                                easy_linear_polynomials_func)
 from .statistics import used_vars_set
-from warnings import warn
-import os
 
 
 class GeneratorLimitExceeded(Exception):
@@ -69,9 +70,8 @@ def build_and_print_matrices(v, strat):
             assert j < cols
             im.putpixel((j, i), 0)
 
-    file_name = strat.matrix_prefix + str(mat_counter) + ".png"
-    if os.path.exists(file_name):
-        os.remove(file_name)
+    file_name = Path(strat.matrix_prefix + str(mat_counter) + ".png")
+    file_name.unlink(missing_ok=True)
     im.save(file_name)
     del im
 
@@ -84,8 +84,8 @@ def multiply_polynomials(l, ring):
     TESTS::
 
         sage: from sage.rings.polynomial.pbori import *
-        sage: r=Ring(1000)
-        sage: x=r.variable
+        sage: r = Ring(1000)
+        sage: x = r.variable
         sage: from sage.rings.polynomial.pbori.nf import multiply_polynomials
         sage: multiply_polynomials([x(3), x(2)+x(5)*x(6), x(0), x(0)+1], r)
         0
@@ -149,9 +149,8 @@ def build_and_print_matrices_deg_colored(v, strat):
             assert j < cols
             hsl = str(270 - (270 * i2deg[j]) / max_deg)
             im.putpixel((j, i), ImageColor.getrgb("hsl(" + hsl + ",100%,50%)"))
-    file_name = strat.matrix_prefix + str(mat_counter) + ".png"
-    if os.path.exists(file_name):
-        os.remove(file_name)
+    file_name = Path(strat.matrix_prefix + str(mat_counter) + ".png")
+    file_name.unlink(missing_ok=True)
     im.save(file_name)
     del im
 

src/sage/sat/solvers/dimacs.py

@@ -28,14 +28,14 @@
 #                  https://www.gnu.org/licenses/
 ##############################################################################
 
-import os
+from pathlib import Path
 import sys
 import subprocess
 import shlex
+from time import sleep
 
 from sage.sat.solvers.satsolver import SatSolver
 from sage.misc.temporary_file import tmp_filename
-from time import sleep
 
 
 class DIMACS(SatSolver):
@@ -44,7 +44,7 @@ class DIMACS(SatSolver):
 
     .. NOTE::
 
-        Usually, users won't have to use this class directly but some
+        Usually, users will not have to use this class directly but some
         class which inherits from this class.
 
     .. automethod:: __init__
@@ -136,10 +136,9 @@ def __del__(self):
         """
         if not self._tail.closed:
             self._tail.close()
-        if os.path.exists(self._tail.name):
-            os.unlink(self._tail.name)
-        if self._headname_file_created_during_init and os.path.exists(self._headname):
-            os.unlink(self._headname)
+        Path(self._tail.name).unlink(missing_ok=True)
+        if self._headname_file_created_during_init:
+            Path(self._headname).unlink(missing_ok=True)
 
     def var(self, decision=None):
         """
@@ -209,7 +208,7 @@ def add_clause(self, lits):
                 self.var()
             l.append(str(lit))
         l.append("0\n")
-        self._tail.write(" ".join(l) )
+        self._tail.write(" ".join(l))
         self._lit += 1
 
     def write(self, filename=None):
@@ -246,19 +245,19 @@ def write(self, filename=None):
         headname = self._headname if filename is None else filename
         head = open(headname, "w")
         head.truncate(0)
-        head.write("p cnf %d %d\n" % (self._var,self._lit))
+        head.write("p cnf %d %d\n" % (self._var, self._lit))
         head.close()
 
         tail = self._tail
         tail.close()
 
-        head = open(headname,"a")
+        head = open(headname, "a")
         tail = open(self._tail.name)
         head.write(tail.read())
         tail.close()
         head.close()
 
-        self._tail = open(self._tail.name,"a")
+        self._tail = open(self._tail.name, "a")
         return headname
 
     def clauses(self, filename=None):
@@ -313,7 +312,7 @@ def clauses(self, filename=None):
                     if lit == 0:
                         break
                     clause.append(lit)
-                clauses.append( ( tuple(clause), False, None ) )
+                clauses.append((tuple(clause), False, None))
             tail.close()
             self._tail = open(self._tail.name, "a")
             return clauses
@@ -362,20 +361,19 @@ def render_dimacs(clauses, filename, nlits):
             1 2 -3 0
             <BLANKLINE>
         """
-        fh = open(filename, "w")
-        fh.write("p cnf %d %d\n" % (nlits,len(clauses)))
-        for clause in clauses:
-            if len(clause) == 3 and clause[1] in (True, False) and clause[2] in (True,False,None):
-                lits, is_xor, rhs = clause
-            else:
-                lits, is_xor, rhs = clause, False, None
-
-            if is_xor:
-                closing = lits[-1] if rhs else -lits[-1]
-                fh.write("x" + " ".join(map(str, lits[:-1])) + " %d 0\n" % closing)
-            else:
-                fh.write(" ".join(map(str, lits)) + " 0\n")
-        fh.close()
+        with open(filename, "w") as fh:
+            fh.write("p cnf %d %d\n" % (nlits, len(clauses)))
+            for clause in clauses:
+                if len(clause) == 3 and clause[1] in (True, False) and clause[2] in (True, False, None):
+                    lits, is_xor, rhs = clause
+                else:
+                    lits, is_xor, rhs = clause, False, None
+
+                if is_xor:
+                    closing = lits[-1] if rhs else -lits[-1]
+                    fh.write("x" + " ".join(map(str, lits[:-1])) + " %d 0\n" % closing)
+                else:
+                    fh.write(" ".join(map(str, lits)) + " 0\n")
 
     def _run(self):
         r"""

src/sage/schemes/elliptic_curves/ec_database.py

@@ -67,7 +67,7 @@
 which enable easy looping through the Cremona elliptic curve database.
 """
 
-import os
+from pathlib import Path
 from ast import literal_eval
 
 from .constructor import EllipticCurve
@@ -132,10 +132,9 @@ def rank(self, rank, tors=0, n=10, labels=False):
         """
         from sage.features.databases import DatabaseEllcurves
         db = DatabaseEllcurves()
-        data = os.path.join(os.path.dirname(db.absolute_filename()),
-                            f'rank{rank}')
+        data = Path(db.absolute_filename()).parent / f'rank{rank}'
         try:
-            f = open(data)
+            f = data.open()
         except OSError:
             return []
         v = []