@app.route('/some_path', methods=['GET,POST'])
def some_method():
    if request.method == 'POST':
        // POST用の処理
    else:
        // GET用の処理

@app.route('/some_path', methods=['GET'])
def get_some_path():
   // GET用の処理

@app.route('/some_path', methods=['POST'])
def post_some_path():
    // POST用の処理