"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
"""


"""
1.from __future__ import absolute_import
for namespace control, pkg with name confilction should import from project

pkg/
pkg/__init__.py
pkg/main.py
pkg/string.py

import string来引入系统的标准string.py, 而用from pkg import string
"""

"""
>>> 3/4
0
>>> from __future__ import division
>>> 3/4
0.75
"""

"""
from __future__ import print_function
在开头加上这句之后，即使在python2.X，使用print就得像python3.X那样加括号使用。
"""