Flask应用程序在heroku上部署并尝试打开excel文件时出错

Question

我有一个Flask应用程序，在该应用程序中，我有一个使用xlsxwriter编写和保存Excel文件的视图。当我在本地运行应用程序时，它工作得非常好。当我部署它时，除了我正在编写Excel文件的视图外，所有视图都正常工作，这会给我错误500。在日志中，我发现错误是我试图使用仅适用于windows的功能启动该文件，有人能告诉我如何启动或下载该文件吗？我不需要将其存储在数据库或云存储中，只需要立即打印或下载即可。如果我问这个问题时出错，请原谅

@app.route("/proverka", methods=['GET', 'POST'])
def proverka():
    stream = artikli.query.all()

    mah_id=db.session.query(db.func.max(info.id)).first()
    s=info.query.filter_by(id=mah_id[0]).first()
    if request.method=='POST':

        workbook = xlsxwriter.Workbook('ISPRATNICI\\{}, {}.xlsx'.format(s.id, s.ime))
        brojac=9
        worksheet = workbook.add_worksheet()
        #NASLOV
        merge_format = workbook.add_format({'align': 'center', "size": "30"})
        worksheet.merge_range('A1:F1',"„Оска-Пром“ Дооел Виница" , merge_format)
        #informacii za firmata
        worksheet.write("B3", "ул. Страшо Пинџур бр.2")
        worksheet.write("B4", "033/363-841")
        worksheet.write("B5", "071-229-482")
        #informacii za kupuvacot
        podatoci_format = workbook.add_format({'align': 'center', "size": "13"})
        worksheet.merge_range('D3:E3',s.ime, podatoci_format)
        worksheet.merge_range('D4:E4',s.kontakt, podatoci_format)
        worksheet.merge_range('D5:E5', s.ulica, podatoci_format)
        #Ispratnica br.
        ispratnica_format = workbook.add_format({'align': 'center', "size": "20"})

        worksheet.merge_range('A8:F8',"Испратница бр. {}".format(s.id) , ispratnica_format)

        #kategorii  
        meni_format = workbook.add_format({'align': 'center', "size":"14", "border":1})
        vkupno=workbook.add_format({"border":1,'align': 'center', "size":"14",  })
        worksheet.write("A9", "р.бр.", meni_format)
        worksheet.write("B9", "Назив на артикл", meni_format)
        worksheet.write("C9", "Количина", meni_format)
        worksheet.write("D9", "Цена", meni_format)
        worksheet.write("E9", "Износ", meni_format)
        worksheet.write("D39", "Вкупно", vkupno)

        worksheet.set_column("A:A", 7.43)
        worksheet.set_column("B:B", 32)
        worksheet.set_column("C:E", 12)
        worksheet.set_row(7, 38)

        #tabeli granica
        granica=workbook.add_format({"border":1})
        #artikli
        for i in stream:
            worksheet.write(brojac, 0, i.id, granica)
            worksheet.write(brojac, 1, i.model, granica)
            worksheet.write(brojac, 2, i.kolicina, granica)
            worksheet.write(brojac,3, i.cena, granica)
            worksheet.write(brojac, 4, i.vkupno, granica)
            brojac+=1
            saldo=workbook.add_format({"align":"center", "size":"16", "border":2})
            worksheet.write_formula('E39', '=SUM(E9:E38)', saldo)
        workbook.close()

        for i in stream:
            kolicini_za_menjanje=magacin.query.filter_by(model=i.model).first()
            print(kolicini_za_menjanje.kolicina)
            nova_kol=kolicini_za_menjanje.kolicina-i.kolicina
            print(nova_kol)
            kolicini_za_menjanje.kolicina = nova_kol
            db.session.commit()

        #IZBRISI ARTIKLI
        brisi=artikli.query.all()
        for i in brisi:
            artikli.query.filter_by(id=i.id).delete()
            db.session.commit()
        os.startfile("C:\\Users\\Nenad\\Desktop\\magacin vs\\ISPRATNICI\\{}, {}.xlsx".format(s.id, s.ime))
        return redirect(url_for("home"))

    return render_template("proverka.html", stream=stream, s=s)

日志：

2020-02-22T16:10:18.789403+00:00 app[web.1]: [2020-02-22 16:10:18,787] ERROR in app: Exception on /proverka [POST]
2020-02-22T16:10:18.789405+00:00 app[web.1]: Traceback (most recent call last):
2020-02-22T16:10:18.789406+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app  
2020-02-22T16:10:18.789407+00:00 app[web.1]: response = self.full_dispatch_request()
2020-02-22T16:10:18.789408+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
2020-02-22T16:10:18.789408+00:00 app[web.1]: rv = self.handle_user_exception(e)
2020-02-22T16:10:18.789408+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
2020-02-22T16:10:18.789409+00:00 app[web.1]: reraise(exc_type, exc_value, tb)
2020-02-22T16:10:18.789409+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise 
2020-02-22T16:10:18.789410+00:00 app[web.1]: raise value
2020-02-22T16:10:18.789410+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
2020-02-22T16:10:18.789411+00:00 app[web.1]: rv = self.dispatch_request()
2020-02-22T16:10:18.789411+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
2020-02-22T16:10:18.789412+00:00 app[web.1]: return self.view_functions[rule.endpoint](**req.view_args)
2020-02-22T16:10:18.789413+00:00 app[web.1]: File "/app/app.py", line 206, in proverka
2020-02-22T16:10:18.789413+00:00 app[web.1]: os.startfile("C:\\Users\\Nenad\\Desktop\\magacin vs\\ISPRATNICI\\{}, {}.xlsx".format(s.id, s.ime))
2020-02-22T16:10:18.789414+00:00 app[web.1]: AttributeError: module 'os' has no attribute 'startfile'
2020-02-22T16:10:18.790447+00:00 app[web.1]: 10.102.224.122 - - [22/Feb/2020:16:10:18 +0000] "POST /proverka HTTP/1.1" 500 290 "https://oska-prom.herokuapp.com/proverka" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36"
2020-02-22T16:10:18.790269+00:00 heroku[router]: at=info method=POST path="/proverka" host=oska-prom.herokuapp.com request_id=4012bbf1-c4ec-46e9-bfd0-5d8fdb23c23d fwd="77.29.30.58" dyno=web.1 connect=0ms service=43ms status=500 bytes=470 protocol=https
2020-02-22T16:10:19.267659+00:00 heroku[router]: at=info method=GET path="/proverka" host=oska-prom.herokuapp.com request_id=ee6b17a9-a2b0-4b77-adaf-d967c48ace12 fwd="77.29.30.58" dyno=web.1 connect=0ms service=15ms status=200 bytes=2539 protocol=https
2020-02-22T16:10:19.269189+00:00 app[web.1]: 10.102.224.122 - - [22/Feb/2020:16:10:19 +0000] "GET /proverka HTTP/1.1" 200 2377 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36"

编辑 我上传了错误所在视图的代码。您能否建议另一种方法，替换硬编码路径或如何下载文件

我想做的是用数据库中的数据创建excel电子表格，然后我想让用户打印或下载到他的计算机上

Answer 1

您硬编码了路径：

os.startfile("C:\\Users\\Nenad\\Desktop\\magacin vs\\ISPRATNICI\\{}, {}.xlsx".format(s.id, s.ime))

使用os可以构建一个相对路径，使其在Windows和Linux上都能工作。我们需要查看源代码来建议您如何正确构建路径

这么说来，您似乎正在将数据写入一个文件中，您可能稍后会使用该文件。Heroku不适合这样做

https://devcenter.heroku.com/articles/dynos#ephemeral-filesystem

Each dyno gets its own ephemeral filesystem, with a fresh copy of the most recently deployed code. During the dyno’s lifetime its running processes can use the filesystem as a temporary scratchpad, but no files that are written are visible to processes in any other dyno and any files written will be discarded the moment the dyno is stopped or restarted. For example, this occurs any time a dyno is replaced due to application deployment and approximately once a day as part of normal dyno management.

Dynos每天重新启动一次。这意味着您的数据将丢失。您需要一个合适的数据库或使用另一个托管解决方案

Answer 2

What I want to do is to create excel spreadsheet with data from the database, and then I want the user to print it or download it on his computer

os.startfile()永远不会这样做

它可能看起来像是在开发中，但这只是因为您的客户机和服务器运行在同一台机器上。如果您在Windows（存在os.startfile()）上托管代码并从另一台计算机连接到它，您的服务器将尝试打开该文件。它根本不会出现在客户机上

除掉

os.startfile("C:\\Users\\Nenad\\Desktop\\magacin vs\\ISPRATNICI\\{}, {}.xlsx".format(s.id, s.ime))

完全是

而是以^{}结束函数：

from flask import send_file

@app.route("/proverka", methods=['GET', 'POST'])
def proverka():
    # ...
    send_file('ISPRATNICI\\{}, {}.xlsx'.format(s.id, s.ime))

正如Tin所指出的，Heroku's filesystem is ephemeral因此服务器上的PDF将消失。如果可以的话，你可能不会遇到太多的问题。如果有人在dyno重新启动之前请求PDF，您可能会遇到一些问题，但他们应该能够再次请求