- Step 1: Read http://www.python.org/dev/peps/pep-0008/
- Step 2: Read http://www.python.org/dev/peps/pep-0008/ again
- Step 3: Read on
Put two newlines between top-level code (funcs, classes, etc)
Use only UNIX style newlines ("n"), not Windows style ("rn")
Put one newline between methods in classes and anywhere else
Long lines should be wrapped in parentheses in preference to using a backslash for line continuation.
Do not write "except:", use "except Exception:" at the very least
Include your name with TODOs as in "#TODO(termie)"
Do not shadow a built-in or reserved word. Example:
def list(): return [1, 2, 3] mylist = list() # BAD, shadows `list` built-in class Foo(object): def list(self): return [1, 2, 3] mylist = Foo().list() # OKAY, does not shadow built-inUse the "is not" operator when testing for unequal identities. Example:
if not X is Y: # BAD, intended behavior is ambiguous pass if X is not Y: # OKAY, intuitive passUse the "not in" operator for evaluating membership in a collection. Example:
if not X in Y: # BAD, intended behavior is ambiguous pass if X not in Y: # OKAY, intuitive pass if not (X in Y or X in Z): # OKAY, still better than all those 'not's pass
- Do not import objects, only modules (*)
- Do not import more than one module per line (*)
- Do not use wildcard
*import (*) - Do not make relative imports
- Do not make new nova.db imports in nova/virt/*
- Order your imports by the full module path
- Organize your imports according to the following template
(*) exceptions are:
- imports from
migratepackage - imports from
sqlalchemypackage - imports from
nova.db.sqlalchemy.sessionmodule - imports from
nova.db.sqlalchemy.migration.versioning_apipackage
Example:
# vim: tabstop=4 shiftwidth=4 softtabstop=4
{{stdlib imports in human alphabetical order}}
\n
{{third-party lib imports in human alphabetical order}}
\n
{{nova imports in human alphabetical order}}
\n
\n
{{begin your code}}
Example:
import httplib import logging import random import StringIO import time import unittest import eventlet import webob.exc import nova.api.ec2 from nova.api import openstack from nova.auth import users from nova.endpoint import cloud import nova.flags from nova import test
Example:
"""A one line docstring looks like this and ends in a period.""" """A multi line docstring has a one-line summary, less than 80 characters. Then a new paragraph after a newline that explains in more detail any general information about the function, class or method. Example usages are also great to have here if it is a complex class for function. When writing the docstring for a class, an extra line should be placed after the closing quotations. For more in-depth explanations for these decisions see http://www.python.org/dev/peps/pep-0257/ 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: the bar parameter :returns: return_type -- description of the return value :returns: description of the return value :raises: AttributeError, KeyError """
If a dictionary (dict) or list object is longer than 80 characters, its items should be split with newlines. Embedded iterables should have their items indented. Additionally, the last item in the dictionary should have a trailing comma. This increases readability and simplifies future diffs.
Example:
my_dictionary = {
"image": {
"name": "Just a Snapshot",
"size": 2749573,
"properties": {
"user_id": 12,
"arch": "x86_64",
},
"things": [
"thing_one",
"thing_two",
],
"status": "ACTIVE",
},
}
Calls to methods 80 characters or longer should format each argument with newlines. This is not a requirement, but a guideline:
unnecessarily_long_function_name('string one',
'string two',
kwarg1=constants.ACTIVE,
kwarg2=['a', 'b', 'c'])
Rather than constructing parameters inline, it is better to break things up:
list_of_strings = [
'what_a_long_string',
'not as long',
]
dict_of_numbers = {
'one': 1,
'two': 2,
'twenty four': 24,
}
object_one.call_a_method('string three',
'string four',
kwarg1=list_of_strings,
kwarg2=dict_of_numbers)
In order to support multiple languages, we have a mechanism to support automatic translations of exception and log strings.
Example:
msg = _("An error occurred")
raise HTTPBadRequest(explanation=msg)
If you have a variable to place within the string, first internationalize the template string then do the replacement.
Example:
msg = _("Missing parameter: %s") % ("flavor",)
LOG.error(msg)
If you have multiple variables to place in the string, use keyword parameters. This helps our translators reorder parameters when needed.
Example:
msg = _("The server with id %(s_id)s has no key %(m_key)s")
LOG.error(msg % {"s_id": "1234", "m_key": "imageId"})
For every new feature, unit tests should be created that both test and (implicitly) document the usage of said feature. If submitting a patch for a bug that had no unit test, a new passing unit test should be added. If a submitted bug fix does have a unit test, be sure to add a new one that fails without the patch and passes with the patch.
For more information on creating unit tests and utilizing the testing infrastructure in OpenStack Nova, please read nova/tests/README.rst.
The testing system is based on a combination of tox and testr. The canonical approach to running tests is to simply run the command tox. This will create virtual environments, populate them with depenedencies and run all of the tests that OpenStack CI systems run. Behind the scenes, tox is running testr run --parallel, but is set up such that you can supply any additional testr arguments that are needed to tox. For example, you can run: tox -- --analyze-isolation to cause tox to tell testr to add --analyze-isolation to its argument list.
It is also possible to run the tests inside of a virtual environment you have created, or it is possible that you have all of the dependencies installed locally already. In this case, you can interact with the testr command directly. Running testr run will run the entire test suite. testr run --parallel will run it in parallel (this is the default incantation tox uses.) More information about testr can be found at: http://wiki.openstack.org/testr
A number of modules from openstack-common are imported into the project.
These modules are "incubating" in openstack-common and are kept in sync with the help of openstack-common's update.py script. See:
http://wiki.openstack.org/CommonLibrary#Incubation
The copy of the code should never be directly modified here. Please always update openstack-common first and then run the script to copy the changes across.
OpenStack is a registered trademark of the OpenStack Foundation, and uses the following capitalization:
OpenStack
Using a common format for commit messages will help keep our git history readable. Follow these guidelines:
First, provide a brief summary of 50 characters or less. Summaries of greater then 72 characters will be rejected by the gate.
The first line of the commit message should provide an accurate description of the change, not just a reference to a bug or blueprint. It must be followed by a single blank line.
If the change relates to a specific driver (libvirt, xenapi, qpid, etc...), begin the first line of the commit message with the driver name, lowercased, followed by a colon.
Following your brief summary, provide a more detailed description of the patch, manually wrapping the text at 72 characters. This description should provide enough detail that one does not have to refer to external resources to determine its high-level functionality.
Once you use 'git review', two lines will be appended to the commit message: a blank line followed by a 'Change-Id'. This is important to correlate this commit with a specific review in Gerrit, and it should not be modified.
For further information on constructing high quality commit messages, and how to split up commits into a series of changes, consult the project wiki:
http://wiki.openstack.org/GitCommitMessages