Error while importing Flickr api using Python on Google App Engine

I'm trying to do a really simple Python webservice. It makes a 'photo.search' using the Flickr API and returns the titles and photos' url.

This webservice will be hosted on Google App Engine.

This is what I actually have right now :

import webapp2
from urllib import urlencode, urlopen
from xml.dom import minidom
from google.appengine.api import urlfetch

class MainPage(webapp2.RequestHandler):

  def get(self):
    self.response.headers['Content-Type'] = 'text/plain'

    data = _doget('flickr.photos.search', text='to_search', per_page='2')
    self.response.write('Ok')

  def _prepare_params(params):
    for (key, value) in params.items():
        if isinstance(value, list):
            params[key] = ','.join([item for item in value])
    return params

  def _doget(method, auth=False, **params):

    params = _prepare_params(params)
    url = 'http://flickr.com/services/rest/?api_key=%s&method=%s&%s%s'% \
          ('stackoverflow_key', method, urlencode(params),
                  _get_auth_url_suffix(method, auth, params))

    result = urlfetch.fetch(url)
    minidom.parse(result.content)
    return result

application = webapp2.WSGIApplication([
    ('/', MainPage),
], debug=True)

I'm a beginner at Python, so I apologize if I did huge mistakes :) I tried several tutorials and sample codes that didn't work.

The imports are making a 500 server error

Error: Server Error

The server encountered an error and could not complete your request.
If the problem persists, please report your problem and mention this error message and the query that caused it.

Does anyone can tell me what's wrong with it ?

If anyone have samples code that did the trick, could be nice.

Thanks a lot in advance for your time!! :D

EDIT :

All right, I changed my code, it's way simplier than before, for testing :

import webapp2
from urllib import urlencode, urlopen
from xml.dom import minidom
from google.appengine.ext.webapp.util import run_wsgi_app
import hashlib
import os


HOST = 'http://api.flickr.com'
API = '/services/rest'
API_KEY = 'my_key'


class MainPage(webapp2.RequestHandler):

     def get(self):
        self.response.headers['Content-Type'] = 'text/html'

        data = _doget('flickr.photos.search', auth=False, text='to_search', per_page='1')
        if data:
           self.response.write(data)
        else:
            self.response.write('Error')

 def _doget(method, **params):

    url = '%s%s/?api_key=%s&method=%s&%s&format=json'% \
      (HOST, API, API_KEY, method, urlencode(params))

    res = urlfetch.fetch(url).content

    # Flickr JSON api returns not valid JSON, which wrapped with "jsonFlickrApi(...)", so we get rid of it.
    if 'jsonFlickrApi(' in res:
        return res[14:-1]

    return json.loads(res)

application = webapp2.WSGIApplication([
    ('/', MainPage),
], debug=True)

When I copy/paste this url, it works perfectly. My aim is to return the data as flickr returns it. But still not working. The print isn't even shown :(

Solution

At the first glance your app has several issues:

I suppose HOST should be 'http://api.flickr.com'
Indentation and formatting (: after if and else) in if-else statement in MainPage class
Undefined varibale "photos" in self.response.write(photos)
Undefined functions "_prepare_params", "_get_auth_url_suffix", "_get_data" and variable "debug" in _doget function.
You should call read() method of urlopen result
You should use minidom.parseString
You can use run_wsgi_app to run your app

So here is the working example:

from google.appengine.ext.webapp.util import run_wsgi_app
import webapp2
from urllib import urlencode, urlopen
from xml.dom import minidom
import hashlib
import os

HOST = 'http://api.flickr.com'
API = '/services/rest'
API_KEY = 'my_key'

debug = False

class MainPage(webapp2.RequestHandler):

    def get(self):
        self.response.headers['Content-Type'] = 'text/html'

        data = _doget('flickr.photos.search', auth=False, text='boston', per_page='2')

        if data:
            photos = data.getElementsByTagName("photo")
            for photo in photos:
                farm_id = 1 # ???
                server_id = photo.attributes['server'].value
                photo_id = photo.attributes['id'].value
                secret = photo.attributes['secret'].value
                photo_url = 'http://farm{farm_id}.staticflickr.com/{server_id}/{photo_id}_{secret}.jpg'.format(farm_id=farm_id,                                                                                                         server_id=server_id,                                                                                                         photo_id=photo_id,                                                                                                         secret=secret)
                self.response.write('<img src="{0}">'.format(photo_url))
        else:
            self.response.write('Error')


def _doget(method, auth=False, **params):
    #print "***** do get %s" % method

    params = params
    url = '%s%s/?api_key=%s&method=%s&%s'% \
      (HOST, API, API_KEY, method, urlencode(params))

    #another useful debug print statement
    if debug:
        print "_doget", url

    res = urlopen(url)
    res = res.read()

    return minidom.parseString(res)


application = webapp2.WSGIApplication([('/', MainPage),], debug=True)

def main():
    run_wsgi_app(application)

if __name__ == "__main__":
    main()

To format flickr photo url I used http://www.flickr.com/services/api/misc.urls.html, but I havent found where to get farm_id parameter, I hope you'll manage it by yourself )

Furthermore, it can be easier to use json format by passing 'format=json' to the API request URL and a bit more properly to use GAE urlfetch service:

import json
from google.appengine.api import urlfetch

# ...

class MainPage(webapp2.RequestHandler):
    def get(self):
        # ...
        for photo in data['photos']['photo']:
            farm_id = 1 # ???
            server_id = photo['server']
            photo_id = photo['id']
            secret = photo['secret']
            # ...

def _doget(method, auth=False, **params):
    # ...
    url = '%s%s/?api_key=%s&method=%s&%s&format=json'% \
      (HOST, API, API_KEY, method, urlencode(params))

    res = urlfetch.fetch(url).content

    # Flickr JSON api returns not valid JSON, which wrapped with "jsonFlickrApi(...)", so we get rid of it.
    if 'jsonFlickrApi(' in res:
        return res[14:-1]

    return json.loads(res)