import os
import uploader


class Finder(object):
    """
    You can pass a list of files or a single directory
    It will return two list:
    * valid uploadable files
    * invalid files/directories
    """
    extensions = uploader.VALID_FORMATS

    def __init__(self, elements):
        self.elements = elements
        self.first = elements[0]
        self._valid = None
        self._invalid = None
        self._prefix = None

    @property
    def prefix(self):
        if self._prefix is None:
            self.populate()
        return self._prefix

    @property
    def invalid(self):
        if self._invalid is None:
            self.populate()
        return self._invalid

    @property
    def valid(self):
        if self._valid is None:
            self.populate()
        return self._valid

    def populate(self):
        self._valid, self._invalid = self.parse()
        if self.one_directory():
            self._prefix = self.first

    def parse(self):
        if self.one_directory():
            return self.valid_files_from_dir()
        else:
            return self.valid_files_from_elements()

    def one_directory(self):
        return len(self.elements) == 1 and os.path.isdir(self.first)

    def valid_files_from_dir(self):
        valid = []
        invalid = []
        for element in os.listdir(self.first):
            if element.startswith('.'):
                continue
            elif self.is_valid(element, self.first):
                valid.append(os.path.basename(element))
            else:
                invalid.append(os.path.basename(element))

        return valid, invalid

    def valid_files_from_elements(self):
        valid = []
        invalid = []

        for element in self.elements:
            if self.is_valid(element):
                valid.append(element)
            else:
                invalid.append(element)

        return valid, invalid

    def is_valid(self, element, prefix=''):
        return os.path.isfile(os.path.join(prefix, element)) and self.valid_extension(element)

    def valid_extension(self, element):
        for extension in self.extensions:
            if element.endswith(extension):
                return True
        return False

@@ -3,16 +3,23 @@
 port os%0A
+from . 
 import u

Change import for py3 compatibility