$ pwd
/Users/ethan/coding/python
$ python
> import os             # 记得导入 os 模块
> os.path.abspath('hello.py')
'/Users/ethan/coding/python/hello.py'
> os.path.abspath('web')
'/Users/ethan/coding/python/web'
> os.path.abspath('.')        # 当前目录的绝对路径
'/Users/ethan/coding/python'

> os.path.dirname('/Users/ethan/coding/python/hello.py')
'/Users/ethan/coding/python'
> os.path.dirname('/Users/ethan/coding/python/')
'/Users/ethan/coding/python'
> os.path.dirname('/Users/ethan/coding/python')
'/Users/ethan/coding'

> os.path.basename('/Users/ethan/coding/python/hello.py')
'hello.py'
> os.path.basename('/Users/ethan/coding/python/')
''
> os.path.basename('/Users/ethan/coding/python')
'python'

> os.path.splitext('/Users/ethan/coding/python/hello.py')
('/Users/ethan/coding/python/hello', '.py')
> os.path.splitext('/Users/ethan/coding/python')
('/Users/ethan/coding/python', '')
> os.path.splitext('/Users/ethan/coding/python/')
('/Users/ethan/coding/python/', '')

> os.path.split('/Users/ethan/coding/python/hello.py')
('/Users/ethan/coding/python', 'hello.py')
> os.path.split('/Users/ethan/coding/python/')
('/Users/ethan/coding/python', '')
> os.path.split('/Users/ethan/coding/python')
('/Users/ethan/coding', 'python')

> os.path.isfile('/Users/ethan/coding/python/hello.py')
True
> os.path.isdir('/Users/ethan/coding/python/')
True
> os.path.isdir('/Users/ethan/coding/python')
True
> os.path.isdir('/Users/ethan/coding/python/hello.py')
False

> for root, dirs, files in os.walk('/Users/ethan/coding'):
...   print root
...   print dirs
...   print files
...
/Users/ethan/coding
['python']
[]
/Users/ethan/coding/python
['web2']
['hello.py']
/Users/ethan/coding/python/web2
[]
[]