如何使用相对进口？

Question

如何阅读/billy/var/text.txt到b.py

目录结构是：

/billy/b.py
/billy/var/text.txt
/sally/s.py

s.py

import sys, os
sys.path.append('..')
from billy import b

print('s.py - ' + os.path.dirname(sys.argv[0]))

b.py

import sys, os

print('b.py - ' + os.path.dirname(sys.argv[0]))
ag = open(os.path.dirname(sys.argv[0]) + '//var//text.txt').read()