always get file path relative to my current file path

README.md

-- ~/root
    |--module1
        |--sub_dir1
              |--source.0.ext
        |--source.1.ext
        |--m1.py
    |--module2
        |--source.2.ext
        |--m2.py

# in m1.py
f = FileFinder() # means directory `~/root/module1`
f = f.child('sub_dir1') # means directory `~/root/module1/sub_dir1`
f.file('source.0.ext') # return `~/root/module1/sub_dir1/source.0.ext`
# so , we can get the `source.0.ext` path in one statement:
FileFinder().child('sub_dir1').file('source.0.ext')

# in m2.py
# to get source.0.ext's path
FileFinder().parent.child('module1').child('sub_dir1').file('source.0.ext')

now we can always get file path relative to my current file path :)

filefinder.py

import inspect
import os


class FileFinder(object):
    def __init__(self, current_directory=u'.'):
        if current_directory == u'.' or current_directory == u'':
            frame = inspect.currentframe()
            frame = frame.f_back
            fi = inspect.getframeinfo(frame)
            self._current_directory = os.path.dirname(fi.filename)
        else:
            _c = os.path.expanduser(current_directory)
            if not os.path.isdir(_c) and os.path.isabs(_c):
                raise Exception(u'`current_directory` must be a absolute directory path')
            self._current_directory = _c

    @property
    def path(self):
        return self._current_directory

    @property
    def parent(self):
        _p = os.path.dirname(self._current_directory)
        if _p == self._current_directory:
            raise Exception(u'no more parent directory for %s' % self._current_directory)
        return FileFinder(_p)

    def child(self, directory_name):
        fs = os.listdir(self._current_directory)
        for fname in fs:
            if directory_name == fname:
                _d = os.path.join(self._current_directory, directory_name)
                if os.path.isdir(_d):
                    return FileFinder(_d)
                raise Exception(u'%s in %s is not a directory'%(directory_name, self._current_directory))
        else:
            raise Exception(u'no such directory in directory %s: %s' % (self._current_directory, directory_name))

    def file(self, file_name):
        fs = os.listdir(self._current_directory)
        for fname in fs:
            if file_name == fname:
                return os.path.join(self._current_directory, file_name)
        else:
            raise Exception(u'no such file in directory %s: %s' % (self._current_directory, file_name))