os and os.path modules
======================

https://docs.python.org/3/library/os.html

    import os


    os.mkdir("hello")           create a folder
    os.rmdir("hello")           delete (an empty) folder

    os.listdir(".")             content of the current folder


https://docs.python.org/3/library/os.path.html

    import os

    # no need to `import os.path` in this case
    # after `import os`, `os.path` is also available

    os.path.exists()            Does the entry exist?
    os.path.isfile()            Is the entry a file?
    os.path.isdir()             Is the entry a folder?

    os.remove()                 delete a file


Exercise:

    Write a program that prints the content of the current
    directory.
    First, print the folders (in alphabetical order).
    Then, print the files (in alphabetical order too).