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      1 class OrderedDict(dict):
      2     """
      3     A dictionary that keeps its keys in the order in which they're inserted.
      4     
      5     Copied from Django's SortedDict with some modifications.
      6 
      7     """
      8     def __new__(cls, *args, **kwargs):
      9         instance = super(OrderedDict, cls).__new__(cls, *args, **kwargs)
     10         instance.keyOrder = []
     11         return instance
     12 
     13     def __init__(self, data=None):
     14         if data is None:
     15             data = {}
     16         super(OrderedDict, self).__init__(data)
     17         if isinstance(data, dict):
     18             self.keyOrder = data.keys()
     19         else:
     20             self.keyOrder = []
     21             for key, value in data:
     22                 if key not in self.keyOrder:
     23                     self.keyOrder.append(key)
     24 
     25     def __deepcopy__(self, memo):
     26         from copy import deepcopy
     27         return self.__class__([(key, deepcopy(value, memo))
     28                                for key, value in self.iteritems()])
     29 
     30     def __setitem__(self, key, value):
     31         super(OrderedDict, self).__setitem__(key, value)
     32         if key not in self.keyOrder:
     33             self.keyOrder.append(key)
     34 
     35     def __delitem__(self, key):
     36         super(OrderedDict, self).__delitem__(key)
     37         self.keyOrder.remove(key)
     38 
     39     def __iter__(self):
     40         for k in self.keyOrder:
     41             yield k
     42 
     43     def pop(self, k, *args):
     44         result = super(OrderedDict, self).pop(k, *args)
     45         try:
     46             self.keyOrder.remove(k)
     47         except ValueError:
     48             # Key wasn't in the dictionary in the first place. No problem.
     49             pass
     50         return result
     51 
     52     def popitem(self):
     53         result = super(OrderedDict, self).popitem()
     54         self.keyOrder.remove(result[0])
     55         return result
     56 
     57     def items(self):
     58         return zip(self.keyOrder, self.values())
     59 
     60     def iteritems(self):
     61         for key in self.keyOrder:
     62             yield key, super(OrderedDict, self).__getitem__(key)
     63 
     64     def keys(self):
     65         return self.keyOrder[:]
     66 
     67     def iterkeys(self):
     68         return iter(self.keyOrder)
     69 
     70     def values(self):
     71         return [super(OrderedDict, self).__getitem__(k) for k in self.keyOrder]
     72 
     73     def itervalues(self):
     74         for key in self.keyOrder:
     75             yield super(OrderedDict, self).__getitem__(key)
     76 
     77     def update(self, dict_):
     78         for k, v in dict_.items():
     79             self.__setitem__(k, v)
     80 
     81     def setdefault(self, key, default):
     82         if key not in self.keyOrder:
     83             self.keyOrder.append(key)
     84         return super(OrderedDict, self).setdefault(key, default)
     85 
     86     def value_for_index(self, index):
     87         """Return the value of the item at the given zero-based index."""
     88         return self[self.keyOrder[index]]
     89 
     90     def insert(self, index, key, value):
     91         """Insert the key, value pair before the item with the given index."""
     92         if key in self.keyOrder:
     93             n = self.keyOrder.index(key)
     94             del self.keyOrder[n]
     95             if n < index:
     96                 index -= 1
     97         self.keyOrder.insert(index, key)
     98         super(OrderedDict, self).__setitem__(key, value)
     99 
    100     def copy(self):
    101         """Return a copy of this object."""
    102         # This way of initializing the copy means it works for subclasses, too.
    103         obj = self.__class__(self)
    104         obj.keyOrder = self.keyOrder[:]
    105         return obj
    106 
    107     def __repr__(self):
    108         """
    109         Replace the normal dict.__repr__ with a version that returns the keys
    110         in their sorted order.
    111         """
    112         return '{%s}' % ', '.join(['%r: %r' % (k, v) for k, v in self.items()])
    113 
    114     def clear(self):
    115         super(OrderedDict, self).clear()
    116         self.keyOrder = []
    117 
    118     def index(self, key):
    119         """ Return the index of a given key. """
    120         return self.keyOrder.index(key)
    121 
    122     def index_for_location(self, location):
    123         """ Return index or None for a given location. """
    124         if location == '_begin':
    125             i = 0
    126         elif location == '_end':
    127             i = None
    128         elif location.startswith('<') or location.startswith('>'):
    129             i = self.index(location[1:])
    130             if location.startswith('>'):
    131                 if i >= len(self):
    132                     # last item
    133                     i = None
    134                 else:
    135                     i += 1
    136         else:
    137             raise ValueError('Not a valid location: "%s". Location key '
    138                              'must start with a ">" or "<".' % location)
    139         return i
    140 
    141     def add(self, key, value, location):
    142         """ Insert by key location. """
    143         i = self.index_for_location(location)
    144         if i is not None:
    145             self.insert(i, key, value)
    146         else:
    147             self.__setitem__(key, value)
    148 
    149     def link(self, key, location):
    150         """ Change location of an existing item. """
    151         n = self.keyOrder.index(key)
    152         del self.keyOrder[n]
    153         i = self.index_for_location(location)
    154         try:
    155             if i is not None:
    156                 self.keyOrder.insert(i, key)
    157             else:
    158                 self.keyOrder.append(key)
    159         except Error:
    160             # restore to prevent data loss and reraise
    161             self.keyOrder.insert(n, key)
    162             raise Error
    163