Py3: Fix DeprecationWarning: generator X raised StopIteration for combinat/words

[vklein]

New commits:

​f28b724

Trac #26458: Py3 combinat/words fix deprecation warning ...

[chapoton]

This is working, but I am not convinced at all that this is the right way to do that. @embray, any opinion ?

[vklein]

I agree try: ... except StopIteration are sort of ugly, i use them when i don't find more concise ways to do that.

That being said this syntax is consistent with ​pep-0479

[vklein]

I have a way to avoid try except for abstract_word.py

diff --git a/src/sage/combinat/words/abstract_word.py b/src/sage/combinat/words/abstract_word.py
index 3e36111..16fa382 100644
--- a/src/sage/combinat/words/abstract_word.py
+++ b/src/sage/combinat/words/abstract_word.py
@@ -1370,16 +1370,17 @@ class Word_class(SageObject):
             ...
             TypeError: mod(=a) must be None or an integer
         """
+        if self.is_empty()
+            return
+
         if mod in (None, 0):
             i = iter(self)
             j = iter(self)
+            next(j)
 
-            try:
-                next(j)
-                while True:
-                    yield next(j) - next(i)
-            except StopIteration:
-                return
+            for a, b in zip(i,j):
+                yield a -b
+            return
 
         elif mod in ZZ:
             Zn = Integers(mod)

Tell me what you prefer.

[chapoton]

ok, let it be.

[embray]

This should be re-targeted for 8.5.