According to Knuth, it is better to break *before* a binary operator.

pep-0008.txt

@@ -151,6 +151,9 @@ Acceptable options in this situation include, but are not limited to::
  that_is_another_thing):
  do_something()
 
+(Also see the discussion of whether to break before or after binary
+operators below.)
+
 The closing brace/bracket/parenthesis on multi-line constructs may
 either line up under the first non-whitespace character of the last
 line of list, as in::
@@ -244,20 +247,33 @@ thoughts on the indentation of such multiline ``with``-statements.)
 
 Another such case is with ``assert`` statements.
 
-Make sure to indent the continued line appropriately. The preferred
-place to break around a binary operator is *after* the operator, not
-before it. Some examples::
+Make sure to indent the continued line appropriately.
+
+
+Should a line break before or after a binary operator?
+------------------------------------------------------
+
+For decades the recommended style has been to break after binary
+operators. However, recent reseach unearthed recommendations by
+Donald Knuth to break *before* binary operators, in his writings about
+typesetting [3]_. Therefore it is permissible to break before or
+after a binary operator, as long as the convention is consistent
+locally. For new code Knuth's style is suggested.
+
+Some examples of code beaking before binary Boolean operators::
 
  class Rectangle(Blob):
 
  def __init__(self, width, height,
  color='black', emphasis=None, highlight=0):
- if (width == 0 and height == 0 and
- color == 'red' and emphasis == 'strong' or
- highlight > 100):
+ if (width == 0
+ and height == 0
+ and color == 'red'
+ and emphasis == 'strong'
+ or highlight > 100):
  raise ValueError("sorry, you lose")
- if width == 0 and height == 0 and (color == 'red' or
-  emphasis is None):
+ if (width == 0 and height == 0
+ and (color == 'red' or emphasis is None)):
  raise ValueError("I don't think so -- values are %s, %s" %
  (width, height))
  Blob.__init__(self, width, height,
@@ -709,7 +725,7 @@ The following naming styles are commonly distinguished:
 - ``UPPERCASE``
 - ``UPPER_CASE_WITH_UNDERSCORES``
 - ``CapitalizedWords`` (or CapWords, or CamelCase -- so named because
- of the bumpy look of its letters [3]_). This is also sometimes known
+ of the bumpy look of its letters [4]_). This is also sometimes known
  as StudlyCaps.
 
  Note: When using abbreviations in CapWords, capitalize all the
@@ -1286,11 +1302,11 @@ annotations are changing.
  PEP 484 recommends the use of stub files: .pyi files that are read
  by the type checker in preference of the corresponding .py files.
  Stub files can be distributed with a library, or separately (with
- the library author's permission) through the typeshed repo [4]_.
+ the library author's permission) through the typeshed repo [5]_.
 
 - For code that needs to be backwards compatible, function annotations
  can be added in the form of comments. See the relevant section of
- PEP 484 [5]_.
+ PEP 484 [6]_.
 
 
 .. rubric:: Footnotes
@@ -1311,12 +1327,14 @@ References
 .. [2] Barry's GNU Mailman style guide
  http://barry.warsaw.us/software/STYLEGUIDE.txt
 
-.. [3] http://www.wikipedia.com/wiki/CamelCase
+.. [3] http://rhodesmill.org/brandon/slides/2012-11-pyconca/#laying-down-the-law
+
+.. [4] http://www.wikipedia.com/wiki/CamelCase
 
-.. [4] Typeshed repo
+.. [5] Typeshed repo
  https://github.com/python/typeshed
 
-.. [5] Suggested syntax for Python 2.7 and straddling code
+.. [6] Suggested syntax for Python 2.7 and straddling code
  https://www.python.org/dev/peps/pep-0484/#suggested-syntax-for-python-2-7-and-straddling-code