Python Flask上传文件到服务器上的app文件夹(heroku)

from flask import Flask, request
from werkzeug.utils import secure_filename
import os

app = Flask(__name__)

# 配置文件上传的相关设置
app.config['UPLOAD_FOLDER'] = 'app'
app.config['ALLOWED_EXTENSIONS'] = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'}

# 定义文件上传的路由
@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    if file and allowed_file(file.filename):
        filename = secure_filename(file.filename)
        file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
        return '文件上传成功'
    else:
        return '不允许上传该类型的文件'

# 检查文件扩展名是否允许上传
def allowed_file(filename):
    return '.' in filename and \
           filename.rsplit('.', 1)[1].lower() in app.config['ALLOWED_EXTENSIONS']

if __name__ == '__main__':
    app.run()