OpenStack Messaging (Zaqar)
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Zaqar style commandments


  • Optimize for readability; whitespace is your friend.
  • Use blank lines to group related logic.
  • All classes must inherit from object (explicitly).
  • Use single-quotes for strings unless the string contains a single-quote.
  • Use the double-quote character for blockquotes (""", not ''')


  • In general use comments as "memory pegs" for those coming after you up the trail.
  • Guide the reader though long functions with a comments introducing different sections of the code.
  • Choose clean, descriptive names for functions and variables to make them self-documenting.
  • Add # NOTE(termie): blah blah... comments to clarify your intent, or to explain a tricky algorithm, when it isn't obvious from just reading the code.


  • Don't use single characters in identifiers except in trivial loop variables and mathematical algorithms.
  • Avoid abbreviations, especially if they are ambiguous or their meaning would not be immediately clear to the casual reader or newcomer.


Wrap long lines by using Python's implied line continuation inside parentheses, brackets and braces. Make sure to indent the continued line appropriately. The preferred place to break around a binary operator is after the operator, not before it.


class Rectangle(Blob):

    def __init__(self, width, height,
                 color='black', emphasis=None, highlight=0):

        # More indentation included to distinguish this from the rest.
        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):
            raise ValueError("I don't think so -- values are {0}, {1}".format(
                             width, height))

        msg = ('this is a very long string that goes on and on and on and'
               'on and on and on...')

        super(Rectangle, self).__init__(width, height,
                                        color, emphasis, highlight)


  • Classes and functions may be hoisted into a package namespace, via __init__ files, with some discretion.

More Import Examples


import zaqar.transport.wsgi as wsgi


from zaqar.transport import wsgi


Docstrings are required for all functions and methods.

Docstrings should ONLY use triple-double-quotes (""")

Single-line docstrings should NEVER have extraneous whitespace between enclosing triple-double-quotes.


""" There is some whitespace between the enclosing quotes :( """


"""There is no whitespace between the enclosing quotes :)"""

Docstrings should document default values for named arguments if they're not None

Docstrings that span more than one line should look like this:


"""Single-line summary, right after the opening triple-double-quote.

If you are going to describe parameters and return values, use Sphinx; the
appropriate syntax is as follows.

:param foo: the foo parameter
:param bar: (Default True) the bar parameter
:param foo_long_bar: the foo parameter description is very
  long so we have to split it in multiple lines in order to
  keep things ordered
:returns: return_type -- description of the return value
:returns: description of the return value
:raises ValueError: if the message_body exceeds 160 characters
:raises TypeError: if the message_body is not a basestring

DO NOT leave an extra newline before the closing triple-double-quote.

Creating Unit Tests

NOTE: 100% coverage is required


Use __name__ as the name of your logger and name your module-level logger objects 'LOG':

LOG = logging.getLogger(__name__)