app/taggable/taggable.py
author Lennard de Rijk <ljvderijk@gmail.com>
Fri, 14 Aug 2009 10:28:06 -0700
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permissions -rw-r--r--
Set new Melange version number to 0-5-20090814p1 in app.yaml.template.
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from google.appengine.ext import db
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import string
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class Tag(db.Model):
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  "Google AppEngine model for store of tags."
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  tag = db.StringProperty(required=True)
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  "The actual string value of the tag."
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  added = db.DateTimeProperty(auto_now_add=True)
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  "The date and time that the tag was first added to the datastore."
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  tagged = db.ListProperty(db.Key)
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  "A List of db.Key values for the datastore objects that have been tagged with this tag value."
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  tagged_count = db.IntegerProperty(default=0)
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  "The number of entities in tagged."
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  @classmethod
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  def __key_name(cls, tag_name):
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    return cls.__name__ + '_' + tag_name
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  def remove_tagged(self, key):
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    def remove_tagged_txn():
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      if key in self.tagged:
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        self.tagged.remove(key)
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        self.tagged_count -= 1
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        self.put()
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    db.run_in_transaction(remove_tagged_txn)
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    self.__class__.expire_cached_tags()
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  def add_tagged(self, key):
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    def add_tagged_txn():
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      if key not in self.tagged:
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        self.tagged.append(key)
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        self.tagged_count += 1
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        self.put()
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    db.run_in_transaction(add_tagged_txn)
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    self.__class__.expire_cached_tags()
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  def clear_tagged(self):
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    def clear_tagged_txn():
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      self.tagged = []
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      self.tagged_count = 0
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      self.put()
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    db.run_in_transaction(clear_tagged_txn)
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    self.__class__.expire_cached_tags()
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  @classmethod
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  def get_by_name(cls, tag_name):
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    return cls.get_by_key_name(cls.__key_name(tag_name))
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  @classmethod
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  def get_tags_for_key(cls, key):
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    "Set the tags for the datastore object represented by key."
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    tags = db.Query(cls).filter('tagged =', key).fetch(1000)
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    return tags
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  @classmethod
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  def get_or_create(cls, tag_name):
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    "Get the Tag object that has the tag value given by tag_value."
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    tag_key_name = cls.__key_name(tag_name)
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    existing_tag = cls.get_by_key_name(tag_key_name)
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    if existing_tag is None:
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      # The tag does not yet exist, so create it.
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      def create_tag_txn():
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        new_tag = cls(key_name=tag_key_name, tag=tag_name)
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        new_tag.put()
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        return new_tag
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      existing_tag = db.run_in_transaction(create_tag_txn)
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    return existing_tag
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  @classmethod
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  def get_tags_by_frequency(cls, limit=1000):
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    """Return a list of Tags sorted by the number of objects to 
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    which they have been applied, most frequently-used first. 
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    If limit is given, return only that many tags; otherwise,
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    return all."""
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    tag_list = db.Query(cls).filter('tagged_count >', 0).order(
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        "-tagged_count").fetch(limit)
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    return tag_list
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  @classmethod
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  def get_tags_by_name(cls, limit=1000, ascending=True):
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    """Return a list of Tags sorted alphabetically by the name of the tag.
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    If a limit is given, return only that many tags; otherwise, return all.
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    If ascending is True, sort from a-z; otherwise, sort from z-a."""
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    from google.appengine.api import memcache
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    cache_name = cls.__name__ + '_tags_by_name'
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    if ascending:
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      cache_name += '_asc'
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    else:
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      cache_name += '_desc'
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    tags = memcache.get(cache_name)
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    if tags is None or len(tags) < limit:
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      order_by = "tag"
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      if not ascending:
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        order_by = "-tag"
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      tags = db.Query(cls).order(order_by).fetch(limit)
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      memcache.add(cache_name, tags, 3600)
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    else:
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      if len(tags) > limit:
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        # Return only as many as requested.
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        tags = tags[:limit]
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    return tags
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  @classmethod
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  def popular_tags(cls, limit=5):
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    from google.appengine.api import memcache
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    tags = memcache.get(cls.__name__ + '_popular_tags')
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    if tags is None:
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      tags = cls.get_tags_by_frequency(limit)
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      memcache.add(cls.__name__ + '_popular_tags', tags, 3600)
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    return tags
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  @classmethod
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  def expire_cached_tags(cls):
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    from google.appengine.api import memcache
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    memcache.delete(cls.__name__ + '_popular_tags')
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    memcache.delete(cls.__name__ + '_tags_by_name_asc')
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    memcache.delete(cls.__name__ + '_tags_by_name_desc')
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  def __str__(self):
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    """Returns the string representation of the entity's tag name.
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    """
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    return self.tag
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def tag_property(tag_name):
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  """Decorator that creates and returns a tag property to be used 
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  in Google AppEngine model.
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  Args:
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    tag_name: name of the tag to be created.
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  """
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  def get_tags(self):
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    """"Get a list of Tag objects for all Tags that apply to the
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    specified entity.
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    """
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    if self._tags[tag_name] is None or len(self._tags[tag_name]) == 0:
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      self._tags[tag_name] = self._tag_model[
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          tag_name].get_tags_for_key(self.key())
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    return self._tags[tag_name]
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  def set_tags(self, seed):
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    """Set a list of Tag objects for all Tags that apply to 
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    the specified entity.
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    """
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    import types
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    if type(seed['tags']) is types.UnicodeType:
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      # Convert unicode to a plain string
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      seed['tags'] = str(seed['tags'])
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    if type(seed['tags']) is types.StringType:
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      # Tags is a string, split it on tag_seperator into a list
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      seed['tags'] = string.split(seed['tags'], self.tag_separator)
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    if type(seed['tags']) is types.ListType:
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      get_tags(self)
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      # Firstly, we will check to see if any tags have been removed.
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      # Iterate over a copy of _tags, as we may need to modify _tags
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      for each_tag in self._tags[tag_name][:]:
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        if each_tag not in seed['tags']:
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          # A tag that was previously assigned to this entity is
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          # missing in the list that is being assigned, so we
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          # disassocaite this entity and the tag.
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          each_tag.remove_tagged(self.key())
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          self._tags[tag_name].remove(each_tag)
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      # Secondly, we will check to see if any tags have been added.
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      for each_tag in seed['tags']:
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        each_tag = string.strip(each_tag)
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        if len(each_tag) > 0 and each_tag not in self._tags[tag_name]:
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          # A tag that was not previously assigned to this entity
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          # is present in the list that is being assigned, so we
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          # associate this entity with the tag.
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          tag = self._tag_model[tag_name].get_or_create(
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              seed['scope'], each_tag)
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          tag.add_tagged(self.key())
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          self._tags[tag_name].append(tag)
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    else:
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      raise Exception, "tags must be either a unicode, a string or a list"
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  return property(get_tags, set_tags)
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class Taggable(object):
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  """A mixin class that is used for making GAE Model classes taggable.
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  This is an extended version of Taggable-mixin which allows for 
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  multiple tag properties in the same AppEngine Model class.
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  """
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  def __init__(self, **kwargs):
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    """The constructor class for Taggable, that creates a dictionary of tags.
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    The difference from the original taggable in terms of interface is
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    that, tag class is not used as the default tag model, since we don't
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    have a default tag property created in this class now.
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    Args:
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      kwargs: keywords containing the name of the tags and arguments
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          containing tag model to be used.
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    """
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    self._tags = {}
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    self._tag_model = {}
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    for tag_name in kwargs:
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      self._tags[tag_name] = None
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      self._tag_model[tag_name] = kwargs[tag_name]
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    self.tag_separator = ", "
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  def tags_string(self, tag_name):
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    "Create a formatted string version of this entity's tags"
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    to_str = ""
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    for each_tag in tag_name:
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      to_str += each_tag.tag
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Madhusudan C.S <madhusudancs@gmail.com>
parents:
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   230
      if each_tag != tag_name[-1]:
0ede2f3adbc1 Adds to Melange a tags framework based on taggable-mixin.
Madhusudan C.S <madhusudancs@gmail.com>
parents:
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   231
        to_str += self.tag_separator
0ede2f3adbc1 Adds to Melange a tags framework based on taggable-mixin.
Madhusudan C.S <madhusudancs@gmail.com>
parents:
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   232
    return to_str