= Python 3 support in GRASS
== Python versions
* keep compatibility with 2.7 (may still work with 2.6, but we don't care)
* port to work with 3.5

== Python components include:
* Python Scripting Library
* PyGRASS
* Temporal Library
* ctypes
* wxGUI

== Python Scripting Library ==
Possible approach:
* functions need to accept unicode and return unicode
* functions wrapping Python Popen class (read_command, run_command, ...) will have parameter encoding
 * encoding=None means expects and returns bytes (the current state)
 * encoding='default' means it takes current encoding using utils._get_encoding()
 * encoding='utf-8' takes whatever encoding user specifies, e.g., utf-8 in this case
 * this is similar to [https://docs.python.org/3.6/library/subprocess.html#subprocess.Popen Popen class in Python3.6]
 * by default encoding='default' to enable expected behavior by users, the following example shows Python3 behavior if we keep using bytes instead of unicode:

{{{
# return bytes
ret = read_command('r.what', encoding=None, ...

for item in ret.splitlines():
    line = item.split('|')[3:]

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: a bytes-like object is required, not 'str'

# we would have to use:
for item in ret.splitlines():
    line = item.split(b'|')[3:]
}}}