235 lines
7.9 KiB
Python
235 lines
7.9 KiB
Python
# Copyright (c) 2008-2009 Aryeh Leib Taurog, all rights reserved.
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# Released under the New BSD license.
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"""
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This module contains a base type which provides list-style mutations
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This is akin to UserList, but without specific data storage methods.
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Possible candidate for a more general position in the source tree,
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perhaps django.utils
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Author: Aryeh Leib Taurog.
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"""
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class ListMixin(object):
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"""
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A base class which provides complete list interface
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derived classes should implement the following:
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function _getitem_external(self, i):
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Return single item with index i for general use
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function _getitem_internal(self, i):
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Same as above, but for use within the class [Optional]
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function _set_collection(self, length, items):
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Recreate the entire object
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function _set_single(self, i, value):
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Set the single item at index i to value [Optional]
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If left undefined, all mutations will result in rebuilding
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the object using _set_collection.
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function __len__(self):
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Return the length
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function __iter__(self):
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Return an iterator for the object
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int _minlength:
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The minimum legal length [Optional]
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int _maxlength:
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The maximum legal length [Optional]
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iterable _allowed:
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A list of allowed item types [Optional]
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class _IndexError:
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The type of exception to be raise on invalid index [Optional]
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"""
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_minlength = 0
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_maxlength = None
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_IndexError = IndexError
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### Python initialization and list interface methods ###
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def __init__(self, *args, **kwargs):
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if not hasattr(self, '_getitem_internal'):
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self._getitem_internal = self._getitem_external
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if not hasattr(self, '_set_single'):
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self._set_single = self._set_single_rebuild
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self._assign_extended_slice = self._assign_extended_slice_rebuild
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super(ListMixin, self).__init__(*args, **kwargs)
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def __getitem__(self, index):
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"Gets the coordinates of the point(s) at the specified index/slice."
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if isinstance(index, slice):
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return [self._getitem_external(i) for i in xrange(*index.indices(len(self)))]
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else:
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index = self._checkindex(index)
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return self._getitem_external(index)
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def __delitem__(self, index):
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"Delete the point(s) at the specified index/slice."
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if not isinstance(index, (int, long, slice)):
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raise TypeError("%s is not a legal index" % index)
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# calculate new length and dimensions
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origLen = len(self)
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if isinstance(index, (int, long)):
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index = self._checkindex(index)
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indexRange = [index]
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else:
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indexRange = range(*index.indices(origLen))
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newLen = origLen - len(indexRange)
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newItems = ( self._getitem_internal(i)
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for i in xrange(origLen)
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if i not in indexRange )
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self._rebuild(newLen, newItems)
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def __setitem__(self, index, val):
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"Sets the Geometry at the specified index."
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if isinstance(index, slice):
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self._set_slice(index, val)
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else:
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index = self._checkindex(index)
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self._check_allowed((val,))
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self._set_single(index, val)
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### Public list interface Methods ###
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def append(self, val):
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"Standard list append method"
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self[len(self):] = [val]
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def extend(self, vals):
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"Standard list extend method"
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self[len(self):] = vals
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def insert(self, index, val):
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"Standard list insert method"
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if not isinstance(index, (int, long)):
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raise TypeError("%s is not a legal index" % index)
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self[index:index] = [val]
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def pop(self, index=-1):
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"Standard list pop method"
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result = self[index]
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del self[index]
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return result
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def index(self, val):
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"Standard list index method"
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for i in xrange(0, len(self)):
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if self[i] == val: return i
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raise ValueError('%s not found in object' % str(val))
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def remove(self, val):
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"Standard list remove method"
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del self[self.index(val)]
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def count(self, val):
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"Standard list count method"
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count = 0
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for i in self:
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if val == i: count += 1
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return count
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### Private API routines unique to ListMixin ###
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def _rebuild(self, newLen, newItems):
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if newLen < self._minlength:
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raise ValueError('Must have at least %d items' % self._minlength)
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if self._maxlength is not None and newLen > self._maxlength:
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raise ValueError('Cannot have more than %d items' % self._maxlength)
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self._set_collection(newLen, newItems)
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def _set_single_rebuild(self, index, value):
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self._set_slice(slice(index, index + 1, 1), [value])
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def _checkindex(self, index, correct=True):
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length = len(self)
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if 0 <= index < length:
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return index
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if correct and -length <= index < 0:
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return index + length
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raise self._IndexError('invalid index: %s' % str(index))
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def _check_allowed(self, items):
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if hasattr(self, '_allowed'):
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if False in [isinstance(val, self._allowed) for val in items]:
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raise TypeError('Invalid type encountered in the arguments.')
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def _set_slice(self, index, values):
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"Assign values to a slice of the object"
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try:
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iter(values)
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except TypeError:
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raise TypeError('can only assign an iterable to a slice')
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self._check_allowed(values)
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origLen = len(self)
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valueList = list(values)
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start, stop, step = index.indices(origLen)
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# CAREFUL: index.step and step are not the same!
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# step will never be None
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if index.step is None:
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self._assign_simple_slice(start, stop, valueList)
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else:
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self._assign_extended_slice(start, stop, step, valueList)
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def _assign_extended_slice_rebuild(self, start, stop, step, valueList):
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'Assign an extended slice by rebuilding entire list'
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indexList = range(start, stop, step)
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# extended slice, only allow assigning slice of same size
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if len(valueList) != len(indexList):
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raise ValueError('attempt to assign sequence of size %d '
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'to extended slice of size %d'
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% (len(valueList), len(indexList)))
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# we're not changing the length of the sequence
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newLen = len(self)
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newVals = dict(zip(indexList, valueList))
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def newItems():
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for i in xrange(newLen):
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if i in newVals:
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yield newVals[i]
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else:
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yield self._getitem_internal(i)
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self._rebuild(newLen, newItems())
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def _assign_extended_slice(self, start, stop, step, valueList):
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'Assign an extended slice by re-assigning individual items'
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indexList = range(start, stop, step)
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# extended slice, only allow assigning slice of same size
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if len(valueList) != len(indexList):
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raise ValueError('attempt to assign sequence of size %d '
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'to extended slice of size %d'
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% (len(valueList), len(indexList)))
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for i, val in zip(indexList, valueList):
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self._set_single(i, val)
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def _assign_simple_slice(self, start, stop, valueList):
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'Assign a simple slice; Can assign slice of any length'
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origLen = len(self)
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stop = max(start, stop)
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newLen = origLen - stop + start + len(valueList)
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def newItems():
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for i in xrange(origLen + 1):
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if i == start:
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for val in valueList:
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yield val
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if i < origLen:
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if i < start or i >= stop:
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yield self._getitem_internal(i)
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self._rebuild(newLen, newItems())
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