D:WorkSpaceTest
D:WorkSpaceTest11.py
D:WorkSpaceTest11.txt
 or
D:WorkSpaceTest
                └─01
                    └─ 01.py
                    └─ 01.txt

import os
print os.getcwd()
f = open("01.txt")
print f.read()

atom editor 01.txt

D:WorkSpaceTest
Traceback (most recent call last):
  File "D:WorkSpaceTest11.py", line 5, in <module>
    f = open("01.txt")
IOError: [Errno 2] No such file or directory: '01.txt'

D:WorkSpaceTest1>01.py
D:WorkSpaceTest1
atom editor 01.txt