Question

I use i18n for localization like django does using a custom request handler for switching between different languages and upgrading to python 2.7 this presents trouble since it uses the cookie from django.utils.translation. In worst case I must to move from our custom request handler to some other system that can switch languages for us. Do you have any idea how to resolve this error? Is the django-language cookie still available like before? What are my other alternatives for localization that don’t depend on django? Babel? Could I still use my old .po and .mo files? Should I use some other Cookie class? My custom request handler class:

from django.utils import translation

class I18NHandler(webapp.RequestHandler):   

    def initialize(self, request, response):
        webapp.RequestHandler.initialize(self, request, response)
        self.request.COOKIES = Cookies(self)
        self.request.META = os.environ
        self.reset_language()

    def reset_language(self):

        # Decide the language from Cookies/Headers

        language = translation.get_language_from_request(self.request)
        translation.activate(language)
        self.request.LANGUAGE_CODE = translation.get_language()

        # Set headers in response

        self.response.headers['Content-Language'] = \
            translation.get_language()


class Cookies(UserDict.DictMixin):

    def __init__(self, handler, **policy):
        self.response = handler.response
        self._in = handler.request.cookies
        self.policy = policy
        if 'secure' not in policy \
            and handler.request.environ.get('HTTPS', '').lower() \
            in ['on', 'true']:
            policy['secure'] = True
        self._out = {}

    def __getitem__(self, key):
        if key in self._out:
            return self._out[key]
        if key in self._in:
            return self._in[key]
        raise KeyError(key)

    def __setitem__(self, key, item):
        self._out[key] = item
        self.set_cookie(key, item, **self.policy)

    def __contains__(self, key):
        return key in self._in or key in self._out

    def keys(self):
        return self._in.keys() + self._out.keys()

    def __delitem__(self, key):
        if key in self._out:
            del self._out[key]
            self.unset_cookie(key)
        if key in self._in:
            del self._in[key]
            p = {}
            if 'path' in self.policy:
                p['path'] = self.policy['path']
            if 'domain' in self.policy:
                p['domain'] = self.policy['domain']
            self.delete_cookie(key, **p)

    # begin WebOb functions

    def set_cookie(
        self,
        key,
        value='',
        max_age=None,
        path='/',
        domain=None,
        secure=None,
        httponly=False,
        version=None,
        comment=None,
        ):
        """
        Set (add) a cookie for the response
        """

        cookies = BaseCookie()
        cookies[key] = value
        for (var_name, var_value) in [
            ('max-age', max_age),
            ('path', path),
            ('domain', domain),
            ('secure', secure),
            ('HttpOnly', httponly),
            ('version', version),
            ('comment', comment),
            ]:
            if var_value is not None and var_value is not False:
                cookies[key][var_name] = str(var_value)
            if max_age is not None:
                cookies[key]['expires'] = max_age
        header_value = cookies[key].output(header='').lstrip()
        self.response.headers._headers.append(('Set-Cookie',
                header_value))

    def delete_cookie(
        self,
        key,
        path='/',
        domain=None,
        ):
        """
        Delete a cookie from the client.  Note that path and domain must match
        how the cookie was originally set.
        This sets the cookie to the empty string, and max_age=0 so
        that it should expire immediately.
        """

        self.set_cookie(key, '', path=path, domain=domain, max_age=0)

    def unset_cookie(self, key):
        """
        Unset a cookie with the given name (remove it from the
        response).  If there are multiple cookies (e.g., two cookies
        with the same name and different paths or domains), all such
        cookies will be deleted.
        """

        existing = self.response.headers.get_all('Set-Cookie')
        if not existing:
            raise KeyError('No cookies at all have been set')
        del self.response.headers['Set-Cookie']
        found = False
        for header in existing:
            cookies = BaseCookie()
            cookies.load(header)
            if key in cookies:
                found = True
                del cookies[key]
            header = cookies.output(header='').lstrip()
            if header:
                self.response.headers.add('Set-Cookie', header)
        if not found:
            raise KeyError('No cookie has been set with the name %r'
                           % key)

Error
Trace:

Traceback (most recent call last):
  File "/base/data/home/apps/s~montaoproject/main.354356023835363013/webapp2.py", line 545, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/apps/s~montaoproject/main.354356023835363013/i18n.py", line 781, in get
    cookie_django_language
  File "/base/data/home/apps/s~montaoproject/main.354356023835363013/util.py", line 65, in __setitem__
    self.set_cookie(key, item, **self.policy)
  File "/base/data/home/apps/s~montaoproject/main.354356023835363013/util.py", line 120, in set_cookie
    self.response.headers._headers.append(('Set-Cookie',
AttributeError: ResponseHeaders instance has no attribute '_headers'

Thanks in advance for any suggestion.

Answer 1

I believe this is because WebOb has been upgraded with the new Python 2.7 runtime.

You should use:

res.headers.add('Set-Cookie', header_value)

As pointed in the webob documentation

Note that webapp has also been replaced by webapp2.