python.md

Best Practices for Python

Baseline

• PEP8.
• Django Coding Style.
• Use single-quotes for strings.

Libraries

For consistency, prefer the following libraries to others that perform the same tasks:

• Fabric for project tasks
• Flask for light web apps or Django for heavy web apps
• boto for accessing AWS programmatically
• pytz for manipulating timezones
• psycopg2 for accessing Postgres
• lxml for XML/DOM manipulation
• Requests for working over HTTP

Specifics

• When testing for nulls, always use if foo is None rather than if !foo so foo == 0 does not cause bugs.
• Always initialize and store datetimes in the UTC timezone. Never use naive datetimes for any reason.
• Always use with when accessing resources that need to be closed.
• Always access blocking resources (files, databases) as little as possible.
• When accessing a dictionary element that may not exist, use get(). For example, os.environ.get('DEPLOYMENT_TARGET', None).
• Project settings that will be used by both fabric and other code should be isolated in app_config.py. fabfile.py and Django's settings.py should import from this file to prevent duplication.
• Imports should be organized into three blocks: stdlib modules, third-party modules and our own modules. Each group should be alphabetized.
• Avoid from foo import *. It is the mindkiller.
• Functions that are de facto "private" (only called within a module or only called within a class) should be prefixed with a single _, e.g. _slugify.

Flask

• All views should return with make_response.