text: 
  __all__ = ['BaseConstructor', 'SafeConstructor', 'Constructor',
      'ConstructorError']
  
  from error import *
  from nodes import *
  from composer import *
  
  try:
      import datetime
      datetime_available = True
  except ImportError:
      datetime_available = False
  
  try:
      set
  except NameError:
      from sets import Set as set
  
  import binascii, re, sys
  
  class ConstructorError(MarkedYAMLError):
      pass
  
  class BaseConstructor(Composer):
  
      yaml_constructors = {}
      yaml_multi_constructors = {}
  
      def __init__(self):
          self.constructed_objects = {}
          self.recursive_objects = {}
  
      def check_data(self):
          # If there are more documents available?
          return self.check_node()
  
      def get_data(self):
          # Construct and return the next document.
          if self.check_node():
              return self.construct_document(self.get_node())
  
      def __iter__(self):
          # Iterator protocol.
          while self.check_node():
              yield self.construct_document(self.get_node())
  
      def construct_document(self, node):
          data = self.construct_object(node)
          self.constructed_objects = {}
          self.recursive_objects = {}
          return data
  
      def construct_object(self, node):
          if node in self.constructed_objects:
              return self.constructed_objects[node]
          if node in self.recursive_objects:
              raise ConstructorError(None, None,
                      "found recursive node", node.start_mark)
          self.recursive_objects[node] = None
          constructor = None
          if node.tag in self.yaml_constructors:
              constructor = lambda node: self.yaml_constructors[node.tag](self, node)
          else:
              for tag_prefix in self.yaml_multi_constructors:
                  if node.tag.startswith(tag_prefix):
                      tag_suffix = node.tag[len(tag_prefix):]
                      constructor = lambda node:  \
                              self.yaml_multi_constructors[tag_prefix](self, tag_suffix, node)
                      break
              else:
                  if None in self.yaml_multi_constructors:
                      constructor = lambda node:  \
                              self.yaml_multi_constructors[None](self, node.tag, node)
                  elif None in self.yaml_constructors:
                      constructor = lambda node:  \
                              self.yaml_constructors[None](self, node)
                  elif isinstance(node, ScalarNode):
                      constructor = self.construct_scalar
                  elif isinstance(node, SequenceNode):
                      constructor = self.construct_sequence
                  elif isinstance(node, MappingNode):
                      constructor = self.construct_mapping
                  else:
                      print node.tag
          data = constructor(node)
          self.constructed_objects[node] = data
          del self.recursive_objects[node]
          return data
  
      def construct_scalar(self, node):
          if not isinstance(node, ScalarNode):
              if isinstance(node, MappingNode):
                  for key_node in node.value:
                      if key_node.tag == u'tag:yaml.org,2002:value':
                          return self.construct_scalar(node.value[key_node])
              raise ConstructorError(None, None,
                      "expected a scalar node, but found %s" % node.id,
                      node.start_mark)
          return node.value
  
      def construct_sequence(self, node):
          if not isinstance(node, SequenceNode):
              raise ConstructorError(None, None,
                      "expected a sequence node, but found %s" % node.id,
                      node.start_mark)
          return [self.construct_object(child) for child in node.value]
  
      def construct_mapping(self, node):
          if not isinstance(node, MappingNode):
              raise ConstructorError(None, None,
                      "expected a mapping node, but found %s" % node.id,
                      node.start_mark)
          mapping = {}
          merge = None
          for key_node in node.value:
              if key_node.tag == u'tag:yaml.org,2002:merge':
                  if merge is not None:
                      raise ConstructorError("while constructing a mapping", node.start_mark,
                              "found duplicate merge key", key_node.start_mark)
                  value_node = node.value[key_node]
                  if isinstance(value_node, MappingNode):
                      merge = [self.construct_mapping(value_node)]
                  elif isinstance(value_node, SequenceNode):
                      merge = []
                      for subnode in value_node.value:
                          if not isinstance(subnode, MappingNode):
                              raise ConstructorError("while constructing a mapping",
                                      node.start_mark,
                                      "expected a mapping for merging, but found %s"
                                      % subnode.id, subnode.start_mark)
                          merge.append(self.construct_mapping(subnode))
                      merge.reverse()
                  else:
                      raise ConstructorError("while constructing a mapping", node.start_mark,
                              "expected a mapping or list of mappings for merging, but found %s"
                              % value_node.id, value_node.start_mark)
              elif key_node.tag == u'tag:yaml.org,2002:value':
                  if '=' in mapping:
                      raise ConstructorError("while construction a mapping", node.start_mark,
                              "found duplicate value key", key_node.start_mark)
                  value = self.construct_object(node.value[key_node])
                  mapping['='] = value
              else:
                  key = self.construct_object(key_node)
                  try:
                      duplicate_key = key in mapping
                  except TypeError, exc:
                      raise ConstructorError("while constructing a mapping", node.start_mark,
                              "found unacceptable key (%s)" % exc, key_node.start_mark)
                  if duplicate_key:
                      raise ConstructorError("while constructing a mapping", node.start_mark,
                              "found duplicate key", key_node.start_mark)
                  value = self.construct_object(node.value[key_node])
                  mapping[key] = value
          if merge is not None:
              merge.append(mapping)
              mapping = {}
              for submapping in merge:
                  mapping.update(submapping)
          return mapping
  
      def construct_pairs(self, node):
          if not isinstance(node, MappingNode):
              raise ConstructorError(None, None,
                      "expected a mapping node, but found %s" % node.id,
                      node.start_mark)
          pairs = []
          for key_node in node.value:
              key = self.construct_object(key_node)
              value = self.construct_object(node.value[key_node])
              pairs.append((key, value))
          return pairs
  
      def add_constructor(cls, tag, constructor):
          if not 'yaml_constructors' in cls.__dict__:
              cls.yaml_constructors = cls.yaml_constructors.copy()
          cls.yaml_constructors[tag] = constructor
      add_constructor = classmethod(add_constructor)
  
      def add_multi_constructor(cls, tag_prefix, multi_constructor):
          if not 'yaml_multi_constructors' in cls.__dict__:
              cls.yaml_multi_constructors = cls.yaml_multi_constructors.copy()
          cls.yaml_multi_constructors[tag_prefix] = multi_constructor
      add_multi_constructor = classmethod(add_multi_constructor)
  
  class SafeConstructor(BaseConstructor):
  
      def construct_yaml_null(self, node):
          self.construct_scalar(node)
          return None
  
      bool_values = {
          u'yes':     True,
          u'no':      False,
          u'true':    True,
          u'false':   False,
          u'on':      True,
          u'off':     False,
      }
  
      def construct_yaml_bool(self, node):
          value = self.construct_scalar(node)
          return self.bool_values[value.lower()]
  
      def construct_yaml_int(self, node):
          value = str(self.construct_scalar(node))
          value = value.replace('_', '')
          sign = +1
          if value[0] == '-':
              sign = -1
          if value[0] in '+-':
              value = value[1:]
          if value == '0':
              return 0
          elif value.startswith('0b'):
              return sign*int(value[2:], 2)
          elif value.startswith('0x'):
              return sign*int(value[2:], 16)
          elif value[0] == '0':
              return sign*int(value, 8)
          elif ':' in value:
              digits = [int(part) for part in value.split(':')]
              digits.reverse()
              base = 1
              value = 0
              for digit in digits:
                  value += digit*base
                  base *= 60
              return sign*value
          else:
              return sign*int(value)
  
      inf_value = 1e300000
      nan_value = inf_value/inf_value
  
      def construct_yaml_float(self, node):
          value = str(self.construct_scalar(node))
          value = value.replace('_', '')
          sign = +1
          if value[0] == '-':
              sign = -1
          if value[0] in '+-':
              value = value[1:]
          if value.lower() == '.inf':
              return sign*self.inf_value
          elif value.lower() == '.nan':
              return self.nan_value
          elif ':' in value:
              digits = [float(part) for part in value.split(':')]
              digits.reverse()
              base = 1
              value = 0.0
              for digit in digits:
                  value += digit*base
                  base *= 60
              return sign*value
          else:
              return float(value)
  
      def construct_yaml_binary(self, node):
          value = self.construct_scalar(node)
          try:
              return str(value).decode('base64')
          except (binascii.Error, UnicodeEncodeError), exc:
              raise ConstructorError(None, None,
                      "failed to decode base64 data: %s" % exc, node.start_mark) 
  
      timestamp_regexp = re.compile(
              ur'''^(?P<year>[0-9][0-9][0-9][0-9])
                  -(?P<month>[0-9][0-9]?)
                  -(?P<day>[0-9][0-9]?)
                  (?:(?:[Tt]|[ \t]+)
                  (?P<hour>[0-9][0-9]?)
                  :(?P<minute>[0-9][0-9])
                  :(?P<second>[0-9][0-9])
                  (?:\.(?P<fraction>[0-9]*))?
                  (?:[ \t]*(?:Z|(?P<tz_hour>[-+][0-9][0-9]?)
                  (?::(?P<tz_minute>[0-9][0-9])?)?))?)?$''', re.X)
  
      def construct_yaml_timestamp(self, node):
          value = self.construct_scalar(node)
          match = self.timestamp_regexp.match(node.value)
          values = match.groupdict()
          for key in values:
              if values[key]:
                  values[key] = int(values[key])
              else:
                  values[key] = 0
          fraction = values['fraction']
          if fraction:
              while 10*fraction < 1000000:
                  fraction *= 10
              values['fraction'] = fraction
          stamp = datetime.datetime(values['year'], values['month'], values['day'],
                  values['hour'], values['minute'], values['second'], values['fraction'])
          diff = datetime.timedelta(hours=values['tz_hour'], minutes=values['tz_minute'])
          return stamp-diff
  
      def construct_yaml_omap(self, node):
          # Note: we do not check for duplicate keys, because it's too
          # CPU-expensive.
          if not isinstance(node, SequenceNode):
              raise ConstructorError("while constructing an ordered map", node.start_mark,
                      "expected a sequence, but found %s" % node.id, node.start_mark)
          omap = []
          for subnode in node.value:
              if not isinstance(subnode, MappingNode):
                  raise ConstructorError("while constructing an ordered map", node.start_mark,
                          "expected a mapping of length 1, but found %s" % subnode.id,
                          subnode.start_mark)
              if len(subnode.value) != 1:
                  raise ConstructorError("while constructing an ordered map", node.start_mark,
                          "expected a single mapping item, but found %d items" % len(subnode.value),
                          subnode.start_mark)
              key_node = subnode.value.keys()[0]
              key = self.construct_object(key_node)
              value = self.construct_object(subnode.value[key_node])
              omap.append((key, value))
          return omap
  
      def construct_yaml_pairs(self, node):
          # Note: the same code as `construct_yaml_omap`.
          if not isinstance(node, SequenceNode):
              raise ConstructorError("while constructing pairs", node.start_mark,
                      "expected a sequence, but found %s" % node.id, node.start_mark)
          pairs = []
          for subnode in node.value:
              if not isinstance(subnode, MappingNode):
                  raise ConstructorError("while constructing pairs", node.start_mark,
                          "expected a mapping of length 1, but found %s" % subnode.id,
                          subnode.start_mark)
              if len(subnode.value) != 1:
                  raise ConstructorError("while constructing pairs", node.start_mark,
                          "expected a single mapping item, but found %d items" % len(subnode.value),
                          subnode.start_mark)
              key_node = subnode.value.keys()[0]
              key = self.construct_object(key_node)
              value = self.construct_object(subnode.value[key_node])
              pairs.append((key, value))
          return pairs
  
      def construct_yaml_set(self, node):
          value = self.construct_mapping(node)
          return set(value)
  
      def construct_yaml_str(self, node):
          value = self.construct_scalar(node)
          try:
              return str(value)
          except UnicodeEncodeError:
              return value
  
      def construct_yaml_seq(self, node):
          return self.construct_sequence(node)
  
      def construct_yaml_map(self, node):
          return self.construct_mapping(node)
  
      def construct_yaml_object(self, node, cls):
          state = self.construct_mapping(node)
          data = cls.__new__(cls)
          if hasattr(data, '__setstate__'):
              data.__setstate__(state)
          else:
              data.__dict__.update(state)
          return data
  
      def construct_undefined(self, node):
          raise ConstructorError(None, None,
                  "could not determine a constructor for the tag %r" % node.tag.encode('utf-8'),
                  node.start_mark)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:null',
          SafeConstructor.construct_yaml_null)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:bool',
          SafeConstructor.construct_yaml_bool)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:int',
          SafeConstructor.construct_yaml_int)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:float',
          SafeConstructor.construct_yaml_float)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:binary',
          SafeConstructor.construct_yaml_binary)
  
  if datetime_available:
      SafeConstructor.add_constructor(
              u'tag:yaml.org,2002:timestamp',
              SafeConstructor.construct_yaml_timestamp)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:omap',
          SafeConstructor.construct_yaml_omap)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:pairs',
          SafeConstructor.construct_yaml_pairs)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:set',
          SafeConstructor.construct_yaml_set)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:str',
          SafeConstructor.construct_yaml_str)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:seq',
          SafeConstructor.construct_yaml_seq)
  
  SafeConstructor.add_constructor(
          u'tag:yaml.org,2002:map',
          SafeConstructor.construct_yaml_map)
  
  SafeConstructor.add_constructor(None,
          SafeConstructor.construct_undefined)
  
  class Constructor(SafeConstructor):
  
      def construct_python_str(self, node):
          return self.construct_scalar(node).encode('utf-8')
  
      def construct_python_unicode(self, node):
          return self.construct_scalar(node)
  
      def construct_python_long(self, node):
          return long(self.construct_yaml_int(node))
  
      def construct_python_complex(self, node):
         return complex(self.construct_scalar(node))
  
      def construct_python_tuple(self, node):
          return tuple(self.construct_yaml_seq(node))
  
      def find_python_module(self, name, mark):
          if not name:
              raise ConstructorError("while constructing a Python module", mark,
                      "expected non-empty name appended to the tag", mark)
          try:
              __import__(name)
          except ImportError, exc:
              raise ConstructorError("while constructing a Python module", mark,
                      "cannot find module %r (%s)" % (name.encode('utf-8'), exc), mark)
          return sys.modules[name]
  
      def find_python_name(self, name, mark):
          if not name:
              raise ConstructorError("while constructing a Python object", mark,
                      "expected non-empty name appended to the tag", mark)
          if u'.' in name:
              # Python 2.4 only
              #module_name, object_name = name.rsplit('.', 1)
              items = name.split('.')
              object_name = items.pop()
              module_name = '.'.join(items)
          else:
              module_name = '__builtin__'
              object_name = name
          try:
              __import__(module_name)
          except ImportError, exc:
              raise ConstructorError("while constructing a Python object", mark,
                      "cannot find module %r (%s)" % (module_name.encode('utf-8'), exc), mark)
          module = sys.modules[module_name]
          if not hasattr(module, object_name):
              raise ConstructorError("while constructing a Python object", mark,
                      "cannot find %r in the module %r" % (object_name.encode('utf-8'),
                          module.__name__), mark)
          return getattr(module, object_name)
  
      def construct_python_name(self, suffix, node):
          value = self.construct_scalar(node)
          if value:
              raise ConstructorError("while constructing a Python name", node.start_mark,
                      "expected the empty value, but found %r" % value.encode('utf-8'),
                      node.start_mark)
          return self.find_python_name(suffix, node.start_mark)
  
      def construct_python_module(self, suffix, node):
          value = self.construct_scalar(node)
          if value:
              raise ConstructorError("while constructing a Python module", node.start_mark,
                      "expected the empty value, but found %r" % value.encode('utf-8'),
                      node.start_mark)
          return self.find_python_module(suffix, node.start_mark)
  
      class classobj: pass
  
      def make_python_instance(self, suffix, node,
              args=None, kwds=None, newobj=False):
          if not args:
              args = []
          if not kwds:
              kwds = {}
          cls = self.find_python_name(suffix, node.start_mark)
          if newobj and isinstance(cls, type(self.classobj))  \
                  and not args and not kwds:
              instance = self.classobj()
              instance.__class__ = cls
              return instance
          elif newobj and isinstance(cls, type):
              return cls.__new__(cls, *args, **kwds)
          else:
              return cls(*args, **kwds)
  
      def set_python_instance_state(self, instance, state):
          if hasattr(instance, '__setstate__'):
              instance.__setstate__(state)
          else:
              slotstate = {}
              if isinstance(state, tuple) and len(state) == 2:
                  state, slotstate = state
              if hasattr(instance, '__dict__'):
                  instance.__dict__.update(state)
              elif state:
                  slotstate.update(state)
              for key, value in slotstate.items():
                  setattr(object, key, value)
  
      def construct_python_object(self, suffix, node):
          # Format:
          #   !!python/object:module.name { ... state ... }
          instance = self.make_python_instance(suffix, node, newobj=True)
          state = self.construct_mapping(node)
          self.set_python_instance_state(instance, state)
          return instance
  
      def construct_python_object_apply(self, suffix, node, newobj=False):
          # Format:
          #   !!python/object/apply       # (or !!python/object/new)
          #   args: [ ... arguments ... ]
          #   kwds: { ... keywords ... }
          #   state: ... state ...
          #   listitems: [ ... listitems ... ]
          #   dictitems: { ... dictitems ... }
          # or short format:
          #   !!python/object/apply [ ... arguments ... ]
          # The difference between !!python/object/apply and !!python/object/new
          # is how an object is created, check make_python_instance for details.
          if isinstance(node, SequenceNode):
              args = self.construct_sequence(node)
              kwds = {}
              state = {}
              listitems = []
              dictitems = {}
          else:
              value = self.construct_mapping(node)
              args = value.get('args', [])
              kwds = value.get('kwds', {})
              state = value.get('state', {})
              listitems = value.get('listitems', [])
              dictitems = value.get('dictitems', {})
          instance = self.make_python_instance(suffix, node, args, kwds, newobj)
          if state:
              self.set_python_instance_state(instance, state)
          if listitems:
              instance.extend(listitems)
          if dictitems:
              for key in dictitems:
                  instance[key] = dictitems[key]
          return instance
  
      def construct_python_object_new(self, suffix, node):
          return self.construct_python_object_apply(suffix, node, newobj=True)
  
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/none',
      Constructor.construct_yaml_null)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/bool',
      Constructor.construct_yaml_bool)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/str',
      Constructor.construct_python_str)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/unicode',
      Constructor.construct_python_unicode)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/int',
      Constructor.construct_yaml_int)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/long',
      Constructor.construct_python_long)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/float',
      Constructor.construct_yaml_float)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/complex',
      Constructor.construct_python_complex)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/list',
      Constructor.construct_yaml_seq)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/tuple',
      Constructor.construct_python_tuple)
  
  Constructor.add_constructor(
      u'tag:yaml.org,2002:python/dict',
      Constructor.construct_yaml_map)
  
  Constructor.add_multi_constructor(
      u'tag:yaml.org,2002:python/name:',
      Constructor.construct_python_name)
  
  Constructor.add_multi_constructor(
      u'tag:yaml.org,2002:python/module:',
      Constructor.construct_python_module)
  
  Constructor.add_multi_constructor(
      u'tag:yaml.org,2002:python/object:',
      Constructor.construct_python_object)
  
  Constructor.add_multi_constructor(
      u'tag:yaml.org,2002:python/object/apply:',
      Constructor.construct_python_object_apply)
  
  Constructor.add_multi_constructor(
      u'tag:yaml.org,2002:python/object/new:',
      Constructor.construct_python_object_new)
  
  