@route('/', method=['POST','GET'])
def index():
    if request.method == 'POST':
        print('666')
        f = request.files['file']
        f.save(f.filename)

    return jinja2_template('templates/index.html')

<form action="/" method="post" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit" value="Upload">
</form>