Python3

Porting to Python 3

We're in the process of porting the entire beets codebase to Python 3.x.

Coding conventions

• all python 2 files must contain from __future__ import division, absolute_import, print_function
• exceptions must use except A as B: instead of except A, B:
• str.format() should be used instead of the % operator
• calls to map() should be wrapped in list() when a list is expected as it returns an iter in python 3

PY3 initial support TODO

• add python 3 to trove classification

PY3 only TODO

• remove u' (and u") prefixes
• run 2to3 to make sure we got everything (but be careful of all the list(map()) wraps, we don't need them all)
• audit all calls to open() (or any other I/O) to see if we can read/write them as text vs binary
• remove any PY2/3 version checks and the related code
• remove any usage of six
• remove # -*- coding: utf-8 -*- from all python files
• replace buffer with memoryview
• replace codecs.open with open
• use explicit keyword arg names in function definitions - PY2: def foo(.., **kwargs) -> PY3: def foo(.., arg1=None, arg2=None, ...) as per https://docs.python.org/3.3/tutorial/controlflow.html#arbitrary-argument-lists
• use str.format style ({}) in beets.logger or drop it completely https://docs.python.org/3/whatsnew/3.2.html#logging
• use more 3.x only functions from shutil to replace some of the functions in beets.util https://docs.python.org/3.4/library/shutil.html (TODO: be more specific)