Issue #22493: Inline flags now should be used only at the start of the

regular expression.  Deprecation warning is emitted if uses them in the
middle of the regular expression.

2 files changed, 11 insertions, 6 deletions

diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index 5297f0b..87cd553 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -224,12 +224,8 @@ The special characters are:
    flags are described in :ref:`contents-of-module-re`.) This
    is useful if you wish to include the flags as part of the regular
    expression, instead of passing a *flag* argument to the
-   :func:`re.compile` function.
-
-   Note that the ``(?x)`` flag changes how the expression is parsed. It should be
-   used first in the expression string, or after one or more whitespace characters.
-   If there are non-whitespace characters before the flag, the results are
-   undefined.
+   :func:`re.compile` function.  Flags should be used first in the
+   expression string.
 
 ``(?:...)``
    A non-capturing version of regular parentheses.  Matches whatever regular
diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index 6bb3469..8752b83 100644
--- a/Doc/whatsnew/3.6.rst
+++ b/Doc/whatsnew/3.6.rst
@@ -1124,6 +1124,15 @@ Deprecated features
   that will not be for several Python releases.  (Contributed by Emanuel Barry
   in :issue:`27364`.)
 
+* Inline flags ``(?letters)`` now should be used only at the start of the
+  regular expression.  Inline flags in the middle of the regular expression
+  affects global flags in Python :mod:`re` module.  This is an exception to
+  other regular expression engines that either apply flags to only part of
+  the regular expression or treat them as an error.  To avoid distinguishing
+  inline flags in the middle of the regular expression now emit a deprecation
+  warning.  It will be an error in future Python releases.
+  (Contributed by Serhiy Storchaka in :issue:`22493`.)
+
 
 Deprecated Python behavior
 --------------------------