#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os

class traverse_file:
    """ traverse files """
    def __init__(self, base='.', ext=['.xls', '.xlsx']):
        self.base = base  # base dir
        self.ext = ext    # match file exten
        self.cdir = None  # curent dir
        self.citer = None # current iter
        self.name = None

    def __str__(self):
        return os.path.join(self.name[0], self.name[1])

    def __iter__(self):
        self.cdir = [os.listdir(self.base)]
        self.citer = [iter(self.cdir[-1])]
        self.name = [self.base, '']
        return self

    def __next__(self):
        try:
            while True:
                f = next(self.citer[-1])
                self.name[-1] = f;
                fn = os.path.join(self.name[0], self.name[1])
                if os.path.isfile(fn):
                    if os.path.splitext(f)[-1] in self.ext:
                        return self
                    else:
                        return next(self)
                if os.path.isdir(fn):
                    if len(os.listdir(fn)) == 0:
                        raise StopIteration
                    self.cdir.append(os.listdir(fn))
                    self.citer.append(iter(self.cdir[-1]))
                    self.name[0] = fn
                    return next(self)
        except StopIteration:
            if len(self.cdir) == 1:
                raise StopIteration
            self.cdir.pop()
            self.citer.pop()
            self.name[0] = os.path.split(self.name[0])[0]
            return next(self)

if __name__ == '__main__':
    for n, f in enumerate(traverse_file(), 1):
        print('{}: {}'.format(n, f))