python flask browsing through directory with files

Is it possible to use flask to browse through a directory with files?

My code never seems to work correctly as weird appending between strings happens.

Also I don`t know how to implement a kind of check whether the path is a file or a folder.

Here is my Flask app.route:

@app.route('/files', defaults={'folder': None,'sub_folder': None}, methods=['GET'])
@app.route('/files/<folder>', defaults={'sub_folder': None}, methods=['GET'])
@app.route('/files/<folder>/<sub_folder>', methods=['GET'])

    def files(folder,sub_folder):
        basedir = 'files/'
        directory = ''

        if folder != None:
            directory = directory + '/' + folder

        if sub_folder != None:
            directory = directory + '/' + sub_folder

        files = os.listdir(basedir + directory)

        return render_template('files.html',files=files,directory=basedir + directory,currdir=directory)

and here is my html template, if anyone could give me some pointers it would be greatly appreciated!

<body>
    <h2>Files {{ currdir }}</h2> </br>
    {% for name in files: %}
        <A HREF="{{ directory }}{{ name }}">{{ name }}</A> </br></br>
    {% endfor %}
</body>s.html',files=files,directory=basedir + directory,currdir=directory)

Solution

A path converter (docs link) in the url structure is better than hardcoding all the different possible path structures.

os.path.exists can be used to check if the path is valid and os.path.isfile and os.path.isdir for checking if the path is a file or a directory, respectively.

Endpoint:

@app.route('/', defaults={'req_path': ''})
@app.route('/<path:req_path>')
def dir_listing(req_path):
    BASE_DIR = '/Users/vivek/Desktop'

    # Joining the base and the requested path
    abs_path = os.path.join(BASE_DIR, req_path)

    # Return 404 if path doesn't exist
    if not os.path.exists(abs_path):
        return abort(404)

    # Check if path is a file and serve
    if os.path.isfile(abs_path):
        return send_file(abs_path)

    # Show directory contents
    files = os.listdir(abs_path)
    return render_template('files.html', files=files)

Template (Now with directory browsing :) ):

<ul>
    {% for file in files %}
    <li>
        <a href="{{ (request.path + '/' if request.path != '/' else '') + file }}">
            {{ (request.path + '/' if request.path != '/' else '') + file }}
        </a>
    </li>
    {% endfor %}
</ul>

Note: abort and send_file functions were imported from flask.