[Python-checkins] bpo-30754: Document textwrap.dedent blank line behavior. (GH-14469)

[Miss Islington (bot)]

https://github.com/python/cpython/commit/e2e41cd114ae761fbfee4e7c6539f5df5c8c7116
commit: e2e41cd114ae761fbfee4e7c6539f5df5c8c7116
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2019-06-29T21:38:11-07:00
summary:

bpo-30754: Document textwrap.dedent blank line behavior. (GH-14469)


* Added documentation for textwrap.dedent behavior.
* Remove an obsolete note about pre-2.5 behavior from the docstring.
(cherry picked from commit eb97b9211e7c99841d6cae8c63893b3525d5a401)

Co-authored-by: tmblweed <tmblweed at users.noreply.github.com>

files:
M Doc/library/textwrap.rst
M Lib/textwrap.py

diff --git a/Doc/library/textwrap.rst b/Doc/library/textwrap.rst
index d254466c9a32..0f11ef401569 100644
--- a/Doc/library/textwrap.rst
+++ b/Doc/library/textwrap.rst
@@ -77,6 +77,9 @@ functions should be good enough; otherwise, you should use an instance of
    equal: the lines ``"  hello"`` and ``"\thello"`` are considered to have no
    common leading whitespace.
 
+   Lines containing only whitespace are ignored in the input and normalized to a
+   single newline character in the output.
+
    For example::
 
       def test():
diff --git a/Lib/textwrap.py b/Lib/textwrap.py
index 8103f347452d..30e693c8de03 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -420,9 +420,9 @@ def dedent(text):
 
     Note that tabs and spaces are both treated as whitespace, but they
     are not equal: the lines "  hello" and "\\thello" are
-    considered to have no common leading whitespace.  (This behaviour is
-    new in Python 2.5; older versions of this module incorrectly
-    expanded tabs before searching for common leading whitespace.)
+    considered to have no common leading whitespace.
+
+    Entirely blank lines are normalized to a newline character.
     """
     # Look for the longest leading string of spaces and tabs common to
     # all lines.