使用带有 Python 的谷歌应用引擎上传图片答案

【问题标题】：Uploading Images using google app engine with Python使用带有 Python 的谷歌应用引擎上传图片
【发布时间】：2014-10-15 06:03:52
【问题描述】：

我正在尝试使用带有 Python 的 google-app-engine 上传图片。我尝试了https://developers.google.com/appengine/docs/python/images/usingimages中的示例“ 谁能解释我如何使用 google-app-engine 上传图片？谢谢！
日志：
文件“C:\Program Files\Google\google_appengine\google\appengine\api\datastore_types.py”，第 382 行，在 __ init __ raise datastore_errors.BadKeyError('无效的字符串键 %s。' % 编码)

BadKeyError：无效的字符串键
代码：

import cgi
import datetime
import urllib
import webapp2

from google.appengine.ext import db
from google.appengine.api import images
from google.appengine.api import users


class Greeting(db.Model):
    """Models a Guestbook entry with an author, content, avatar, and date."""
    author = db.StringProperty()
    content = db.StringProperty(multiline=True)
    avatar = db.BlobProperty()
    date = db.DateTimeProperty(auto_now_add=True)


def guestbook_key(guestbook_name=None):
    """Constructs a Datastore key for a Guestbook entity with guestbook_name."""
    return db.Key.from_path('Guestbook', guestbook_name or 'default_guestbook')


class MainPage(webapp2.RequestHandler):
    def get(self):
        self.response.out.write('<html><body>')
        guestbook_name=self.request.get('guestbook_name')

        greetings = db.GqlQuery('SELECT * '
                                'FROM Greeting '
                                'WHERE ANCESTOR IS :1 '
                                'ORDER BY date DESC LIMIT 10',
                                guestbook_key(guestbook_name))

        for greeting in greetings:
            if greeting.author:
                self.response.out.write(
                    '<b>%s</b> wrote:' % greeting.author)
            else:
                self.response.out.write('An anonymous person wrote:')
            self.response.out.write('<div><img src="img?img_id=%s"></img>' %
                                    greeting.key())
            self.response.out.write('<blockquote>%s</blockquote></div>' %
                                    cgi.escape(greeting.content))

        self.response.out.write("""
              <form action="/sign?%s" enctype="multipart/form-data" method="post">
                <div><textarea name="content" rows="3" cols="60"></textarea></div>
                <div><label>Avatar:</label></div>
                <div><input type="file" name="img"/></div>
                <div><input type="submit" value="Sign Guestbook"></div>
              </form>
              <hr>
              <form>Guestbook name: <input value="%s" name="guestbook_name">
              <input type="submit" value="switch"></form>
            </body>
          </html>""" % (urllib.urlencode({'guestbook_name': guestbook_name}),
                        cgi.escape(guestbook_name)))


class Image(webapp2.RequestHandler):
    def get(self):
        greeting = db.get(self.request.get('img_id'))
        if greeting.avatar:
            self.response.headers['Content-Type'] = 'image/png'
            self.response.out.write(greeting.avatar)
        else:
            self.response.out.write('No image')


class Guestbook(webapp2.RequestHandler):
    def post(self):
        guestbook_name = self.request.get('guestbook_name')
        greeting = Greeting(parent=guestbook_key(guestbook_name))

        if users.get_current_user():
            greeting.author = users.get_current_user().nickname()

        greeting.content = self.request.get('content')
        avatar = images.resize(self.request.get('img'), 32, 32)
        greeting.avatar = db.Blob(avatar)
        greeting.put()
        self.redirect('/?' + urllib.urlencode(
            {'guestbook_name': guestbook_name}))


app = webapp2.WSGIApplication([('/', MainPage),
                               ('/img', Image),
                               ('/sign', Guestbook)],
                              debug=True)

【问题讨论】：

您能否包含实际的日志，以便我们查看是哪一行引发了错误。
您只是想运行示例还是进行了一些修改？
我只是想运行这个例子
需要整个堆栈跟踪。我刚刚做了这个例子，它奏效了。请注意，您需要按照说明安装 PIL 库或将库添加到 app.yaml 并部署它。
谢谢！ pil 库我没有安装，我会安装它！

标签： python google-app-engine python-2.7 file-upload image-uploading

【解决方案1】：

您正在使用类似 Jinja 的参数，但您没有填充任何模板，而是使用 python 格式化字符串：

self.response.out.write("""
          <form action="/sign?%s" enctype="multipart/form-data" method="post">
            <div><textarea name="content" rows="3" cols="60"></textarea></div>
            <div><label>Avatar:</label></div>
            <div><input type="file" name="img"/></div>
            <div><input type="submit" value="Sign Guestbook"></div>
          </form>
          <hr>
          <form>Guestbook name: <input value="%s" name="guestbook_name">
          <input type="submit" value="switch"></form>
        </body>
      </html>""" % (urllib.urlencode({'guestbook_name': guestbook_name}),
                    cgi.escape(guestbook_name)))

请注意，您说urrlib.urlenconde({'guestbook_name': guestbook_name})，其中python 只需要一个字符串：guestbook_name。此外，鉴于您对所有可以使用的占位符使用相同的值

"...<input value="%(guestbook)s" name..." % {'guestbook': cgi.escape(guestbook_name)})

或

"...<input value="{0}" name... ...</html>".format(cgi.escape(guestbook_name))

希望对你有帮助。

【讨论】：