Python 3 適用的 Blobstore API

本頁面說明如何在標準環境中，搭配 Python 3 執行階段使用 Blobstore API (其中一項舊版套裝服務)。應用程式可透過 Python 3 專用的 App Engine 服務 SDK 存取套裝組合服務。

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Python 3 不支援 webapp，因此將 Blobstore 處理常式程式碼從 Python 2 遷移至 Python 3 時，您需要進行一些微小變更。如要使用 Python 3 適用的 Blobstore API，請注意下列事項：

• Blobstore 處理常式類別是公用程式類別。也就是說，處理常式類別不再以 webapp 為基礎，您無法使用 webapp 套件 (google.appengine.ext.webapp) 提供的 blobstore_handlers 模組，也無法在這些處理常式的子類別中使用 webapp2.RequestHandler 參數。

• Blobstore 處理常式類別中的所有方法，都需要 WSGI environ 字典做為輸入參數。

以下各節說明如何在 Flask 應用程式和不使用 Python 架構的 WSGI 應用程式中，將 BlobstoreUploadHandler 和 BlobstoreDownloadHandler 類別用於 Python 3。您可以比較 Python 3 範例與 Python 2 範例程式碼，進一步瞭解程式碼變更差異。

範例：Flask 應用程式

在 Python 3 中，Blobstore 處理常式類別屬於 google.appengine.ext.blobstore 模組。如果是 Flask 應用程式，對 BlobstoreUploadHandler 和 BlobstoreDownloadHandler 類別中的方法進行的所有呼叫，都需要 request.environ 字典 (request 是從 flask 模組匯入)。

比較從 Python 2 (webapp2) 到 Python 3 (Flask) 的程式碼變更。請注意 Flask 應用程式如何在 get_uploads() 和 send_blob() 方法中使用 request.environ 參數：

Python 2 (webapp2)

class PhotoUploadHandler(blobstore_handlers.BlobstoreUploadHandler):
    def post(self):
        upload = self.get_uploads()[0]
        user_photo = UserPhoto(
            user=users.get_current_user().user_id(),
            blob_key=upload.key())
        user_photo.put()

        self.redirect('/view_photo/%s' % upload.key())

class ViewPhotoHandler(blobstore_handlers.BlobstoreDownloadHandler):
    def get(self, photo_key):
        if not blobstore.get(photo_key):
            self.error(404)
        else:
            self.send_blob(photo_key)

app = webapp2.WSGIApplication([
    ('/', PhotoUploadFormHandler),
    ('/upload_photo', PhotoUploadHandler),
    ('/view_photo/([^/]+)?', ViewPhotoHandler),
], debug=True)

Python 3 (Flask)

class PhotoUploadHandler(blobstore.BlobstoreUploadHandler):
    def post(self):
        upload = self.get_uploads(request.environ)[0]
        photo = PhotoUpload(blob_key=upload.key())
        photo.put()

        return redirect("/view_photo/%s" % upload.key())


class ViewPhotoHandler(blobstore.BlobstoreDownloadHandler):
    def get(self, photo_key):
        if not blobstore.get(photo_key):
            return "Photo key not found", 404
        else:
            headers = self.send_blob(request.environ, photo_key)

            # Prevent Flask from setting a default content-type.
            # GAE sets it to a guessed type if the header is not set.
            headers["Content-Type"] = None
            return "", headers


@app.route("/view_photo/<photo_key>")
def view_photo(photo_key):
    """View photo given a key."""
    return ViewPhotoHandler().get(photo_key)


@app.route("/upload_photo", methods=["POST"])
def upload_photo():
    """Upload handler called by blobstore when a blob is uploaded in the test."""
    return PhotoUploadHandler().post()

如要查看 Python 3 (Flask) 的完整程式碼範例，請前往 GitHub。

範例：沒有網頁架構的 WSGI 應用程式

下列 Python 3 (WSGI 應用程式) 程式碼說明如何在使用 Blobstore 處理常式類別時，為沒有 Web 架構的 WSGI 應用程式新增 environ 參數。請注意 environ 參數在 get_uploads() 和 send_blob() 方法中的使用方式，並與 Python 2 版本比較：

Python 2

class PhotoUploadHandler(blobstore_handlers.BlobstoreUploadHandler):
    def post(self):
        upload = self.get_uploads()[0]
        user_photo = UserPhoto(
            user=users.get_current_user().user_id(),
            blob_key=upload.key())
        user_photo.put()

        self.redirect('/view_photo/%s' % upload.key())

class ViewPhotoHandler(blobstore_handlers.BlobstoreDownloadHandler):
    def get(self, photo_key):
        if not blobstore.get(photo_key):
            self.error(404)
        else:
            self.send_blob(photo_key)

app = webapp2.WSGIApplication([
    ('/', PhotoUploadFormHandler),
    ('/upload_photo', PhotoUploadHandler),
    ('/view_photo/([^/]+)?', ViewPhotoHandler),
], debug=True)

Python 3

class UploadPhotoHandler(blobstore.BlobstoreUploadHandler):
    """Upload handler called by blobstore when a blob is uploaded in the test."""

    def post(self, environ):
        upload = self.get_uploads(environ)[0]
        user_photo = UserPhoto(blob_key=upload.key())
        user_photo.put()

        # Redirect to the '/view_photo/<Photo Key>' URL
        return (
            "",
            http.HTTPStatus.FOUND,
            [("Location", "/view_photo/%s" % upload.key())],
        )


class ViewPhotoHandler(blobstore.BlobstoreDownloadHandler):
    def get_photo(self, environ, photo_key):
        if not blobstore.get(photo_key):
            return "Photo key not found", http.HTTPStatus.NOT_FOUND, []
        else:
            return (
                "",
                http.HTTPStatus.OK,
                list(self.send_blob(environ, photo_key).items()),
            )

    def get(self, environ):
        photo_key = (environ["app.url_args"])[0]
        return self.get_photo(environ, photo_key)


# map urls to functions
urls = [
    (r"^$", UploadFormHandler),
    (r"upload_photo/?$", UploadPhotoHandler),
    (r"view_photo/(.+)$", ViewPhotoHandler),
]

如要查看 Python 3 的完整程式碼範例，請前往 GitHub。