Trac #27472: py3: import error

This is bug report on python3-build sage.

When attaching a file which loads a pyx file, the reloading fails.

Steps to reproduce:

create a file "test.py" with
{{{
from sage.misc.persist import load
load("anyfile.pyx")

def cool(n):
    return -n
}}}
and a pyx file with the chosen name.

Then attach the test.py file. This should compile the pyx file.

Then modify a function in the test.py file and save it.

Then one gets an error:
{{{
### reloading attached file test.py modified at 16:49:10 ###
  File "<string>", line 1
    from _home_chapoton_anyfile_pyx_0.cpython-36m-x86_64-linux-gnu
import *
            ^
SyntaxError: invalid syntax
}}}

I suspect that maybe the issue is the presence of `-` in the name of the
created python module.

URL: https://trac.sagemath.org/27472
Reported by: chapoton
Ticket author(s): Erik Bray, Frédéric Chapoton
Reviewer(s): François Bissey

src/sage/misc/sageinspect.py

@@ -122,14 +122,22 @@ def foo(unsigned int x=1, a=')"', b={not (2+1==3):'bar'}, *args, **kwds): return
 import inspect
 import functools
 import os
+import sys
 import tokenize
 import re
 EMBEDDED_MODE = False
 from sage.env import SAGE_LIB
 
+try:
+    import importlib.machinery as import_machinery
+except ImportError:
+    pass
+
+
 def loadable_module_extension():
     r"""
     Return the filename extension of loadable modules, including the dot.
+
     It is '.dll' on cygwin, '.so' otherwise.
 
     EXAMPLES::
@@ -138,11 +146,15 @@ def loadable_module_extension():
         sage: sage.structure.sage_object.__file__.endswith(loadable_module_extension())
         True
     """
-    import sys
-    if sys.platform == 'cygwin':
-        return os.path.extsep+'dll'
+    if six.PY2:
+        if sys.platform == 'cygwin':
+            return os.path.extsep + 'dll'
+        else:
+            return os.path.extsep + 'so'
     else:
-        return os.path.extsep+'so'
+        # Return the full platform-specific extension module suffix
+        return import_machinery.EXTENSION_SUFFIXES[0]
+
 
 def isclassinstance(obj):
     r"""
@@ -2093,7 +2105,8 @@ class ParentMethods:
         # the length of lines, which causes an error.  Safeguard against that.
         lnum = min(obj.co_firstlineno,len(lines))-1
         while lnum > 0:
-            if pmatch(lines[lnum]): break
+            if pmatch(lines[lnum]):
+                break
             lnum -= 1
 
         return inspect.getblock(lines[lnum:]), lnum+base_lineno

src/sage/repl/attach.py

@@ -58,15 +58,15 @@
     sage: detach(src)
 """
 
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2013 Volker Braun <vbraun.name@gmail.com>
 #
 # 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 __future__ import print_function
 
 import os
@@ -532,8 +532,8 @@ def modified_file_iterator():
         [('/.../tmp_....py', time.struct_time(...))]
     """
     global attached
-    modified = dict()
-    for filename in attached.keys():
+    modified = {}
+    for filename in list(attached):
         old_tm = attached[filename]
         if not os.path.exists(filename):
             print('### detaching file {0} because it does not exist (deleted?) ###'.format(filename))
@@ -547,7 +547,7 @@ def modified_file_iterator():
         return
     time.sleep(0.1)  # sleep 100ms to give the editor time to finish saving
 
-    for filename in modified.keys():
+    for filename in list(modified):
         old_tm = modified[filename]
         new_tm = os.path.getmtime(filename)
         if new_tm == old_tm: