How to use the xblock.fields.Scope.user_state function in XBlock

def _user_state_key(self):
        return xblock.runtime.KeyValueStore.Key(
            scope=xblock.fields.Scope.user_state, user_id='123',
            block_scope_id='456', field_name='my_field')

def test_for_export_transforms_value_for_student_data(self):
        key = self.get_key(
            xblock.fields.Scope.user_state, '1234567890',
            '0d40c9be8e254416b4782bf8e19a538f', 'my_field')
        orig_model = dbmodels.KeyValueEntity(key=key, data='{"value": 1}')
        safe_model = orig_model.for_export(self.transform)
        self.assertEquals('tr_{"value": 1}', safe_model.data)

def test_slider_block(self):
        """Test peristence of fields in user scope."""
        usage_id = self.runtime.parse_xml_string(
            '', self.id_generator)
        block = self.runtime.get_block(usage_id)

        block.value = 50
        block.save()

        key = xblock.runtime.KeyValueStore.Key(
            scope=xblock.fields.Scope.user_state,
            user_id=self.STUDENT_ID,
            block_scope_id=block.scope_ids.usage_id,
            field_name='value')

        self.assertEqual(50, store.KeyValueStore().get(key))

is_valid = False

        return Response(json={'isValid': is_valid, 'message': message})


@XBlock.needs('modulestore')
class PlaybackStateMixin(XBlock):
    """
    PlaybackStateMixin encapsulates video-playback related data.

    These fields are not visible to end-user.
    """

    current_time = Float(
        default=0,
        scope=Scope.user_state,
        help='Seconds played back after the start'
    )

    playback_rate = Float(
        default=1,
        scope=Scope.preferences,
        help='Supported video playbacks speeds are: 0.5, 1, 1.5, 2'
    )

    volume = Float(
        default=1,
        scope=Scope.preferences,
        help='Video volume: from 0 to 1'
    )

    muted = Boolean(

nb_upload_datetime = String(
        help="UTC datetime the notebook was uploaded",
        scope=Scope.settings,
        default=""
    )

    raw_possible = Float(
        help="Max possible score attainable",
        scope=Scope.settings,
        default=0.0
    )

    # ------- Internal Student Fields -------
    student_attempts = Integer(
        help="Number of times student has submitted problem",
        scope=Scope.user_state,
        default=0
    )

    student_score = Float(
        help="Student Score",
        scope=Scope.user_state,
        default=0
    )

    student_section_scores = List(
        help="Student Scores per section",
        scope=Scope.user_state,
        default=[]
    )

    student_submitted_dt = String(

)
    # save completion_status for SCORM_2004
    lesson_status = String(
        scope=Scope.user_state,
        default='not attempted'
    )
    success_status = String(
        scope=Scope.user_state,
        default='unknown'
    )
    data_scorm = Dict(
        scope=Scope.user_state,
        default={}
    )
    lesson_score = Float(
        scope=Scope.user_state,
        default=0
    )
    weight = Float(
        default=1,
        scope=Scope.settings
    )
    has_score = Boolean(
        display_name=_("Scored"),
        help=_("Select False if this component will not receive a numerical score from the Scorm"),
        default=True,
        scope=Scope.settings
    )
    icon_class = String(
        default="video",
        scope=Scope.settings,
    )

return 'video'


@XBlock.needs('jinja')
class SequenceBlock(XBlock):
    """An XBlock which presents its children in a tabbed view.

    See xmodule.seq_module.SequenceModule in
    https://github.com/edx/edx-platform.
    """

    has_children = True

    position = Integer(
        help='Last tab viewed in this sequence',
        scope=Scope.user_state,
        default=0)

    def __init__(self, *args, **kwargs):
        super(SequenceBlock, self).__init__(*args, **kwargs)
        self.templates_dirs = [os.path.join(os.path.dirname(__file__), 'templates')]
        self.get_template = self.runtime.service(self, 'jinja')

    def student_view(self, context=None):
        frag = Fragment()

        frag.add_css_url(
            self.runtime.local_resource_url(self, 'public/css/sequence.css'))
        frag.add_javascript_url(
            self.runtime.local_resource_url(self, 'public/js/sequence.js'))
        frag.initialize_js('SequenceBlock')

from urlparse import urlparse

from xblock.core import XBlock
from xblock.fields import Scope, Integer, String
from xblock.fragment import Fragment


class SimpleVideoBlock(XBlock):
    """
    An XBlock providing oEmbed capabilities for video (currently only supporting Vimeo)
    """

    href = String(help="URL of the video page at the provider", default=None, scope=Scope.content)
    maxwidth = Integer(help="Maximum width of the video", default=800, scope=Scope.content)
    maxheight = Integer(help="Maximum height of the video", default=450, scope=Scope.content)
    watched_count = Integer(help="The number of times the student watched the video", default=0, scope=Scope.user_state)

    def student_view(self, context):
        """
        Create a fragment used to display the XBlock to a student.
        `context` is a dictionary used to configure the display (unused)

        Returns a `Fragment` object specifying the HTML, CSS, and JavaScript
        to display.
        """
        provider, embed_code = self.get_embed_code_for_url(self.href)

        # Load the HTML fragment from within the package and fill in the template
        html_str = pkg_resources.resource_string(__name__, "static/html/simplevideo.html")
        frag = Fragment(unicode(html_str).format(self=self, embed_code=embed_code))

        # Load CSS

raw_possible = Float(
        help="Max possible score attainable",
        scope=Scope.settings,
        default=0.0
    )

    # ------- Internal Student Fields -------
    student_attempts = Integer(
        help="Number of times student has submitted problem",
        scope=Scope.user_state,
        default=0
    )

    student_score = Float(
        help="Student Score",
        scope=Scope.user_state,
        default=0
    )

    student_section_scores = List(
        help="Student Scores per section",
        scope=Scope.user_state,
        default=[]
    )

    student_submitted_dt = String(
        help="UTC datetime student last submitted notebook",
        scope=Scope.user_state,
        default=""
    )

    editable_fields = ('display_name', 'instructions', 'max_attempts',

def export_xml(self, node):
        node.tag = self.xml_element_name()

        # Set node attributes based on our fields.
        for field_name, field in self.fields.items():
            if field_name in ('children', 'parent', 'content', 'data'):
                continue
            # TODO(jorr): Restore export of user state fields once roundtripping
            # fields of type Dict through XML is fixed. Currently this is broken
            # in XBlock, and so as a work-around ommit all the user_state fields
            # because these happen to be the only ones which are Dicts.
            if field.is_set_on(self) and field.scope is not Scope.user_state:
                node.set(field_name, unicode(field.read_from(self)))

        for child in etree.fromstring(self.data):
            node.append(child)