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# Copyright (c) 2008-2009 Aryeh Leib Taurog, all rights reserved.
# Released under the New BSD license.
"""
This module contains a base type which provides list-style mutations
without specific data storage methods.
See also http://www.aryehleib.com/MutableLists.html
Author: Aryeh Leib Taurog.
"""
from django.utils.functional import total_ordering
@total_ordering
class ListMixin(object):
"""
A base class which provides complete list interface.
Derived classes must call ListMixin's __init__() function
and implement the following:
function _get_single_external(self, i):
Return single item with index i for general use.
The index i will always satisfy 0 <= i < len(self).
function _get_single_internal(self, i):
Same as above, but for use within the class [Optional]
Note that if _get_single_internal and _get_single_internal return
different types of objects, _set_list must distinguish
between the two and handle each appropriately.
function _set_list(self, length, items):
Recreate the entire object.
NOTE: items may be a generator which calls _get_single_internal.
Therefore, it is necessary to cache the values in a temporary:
temp = list(items)
before clobbering the original storage.
function _set_single(self, i, value):
Set the single item at index i to value [Optional]
If left undefined, all mutations will result in rebuilding
the object using _set_list.
function __len__(self):
Return the length
int _minlength:
The minimum legal length [Optional]
int _maxlength:
The maximum legal length [Optional]
type or tuple _allowed:
A type or tuple of allowed item types [Optional]
class _IndexError:
The type of exception to be raise on invalid index [Optional]
"""
_minlength = 0
_maxlength = None
_IndexError = IndexError
### Python initialization and special list interface methods ###
def __init__(self, *args, **kwargs):
if not hasattr(self, '_get_single_internal'):
self._get_single_internal = self._get_single_external
if not hasattr(self, '_set_single'):
self._set_single = self._set_single_rebuild
self._assign_extended_slice = self._assign_extended_slice_rebuild
super(ListMixin, self).__init__(*args, **kwargs)
def __getitem__(self, index):
"Get the item(s) at the specified index/slice."
if isinstance(index, slice):
return [self._get_single_external(i) for i in xrange(*index.indices(len(self)))]
else:
index = self._checkindex(index)
return self._get_single_external(index)
def __delitem__(self, index):
"Delete the item(s) at the specified index/slice."
if not isinstance(index, (int, long, slice)):
raise TypeError("%s is not a legal index" % index)
# calculate new length and dimensions
origLen = len(self)
if isinstance(index, (int, long)):
index = self._checkindex(index)
indexRange = [index]
else:
indexRange = range(*index.indices(origLen))
newLen = origLen - len(indexRange)
newItems = ( self._get_single_internal(i)
for i in xrange(origLen)
if i not in indexRange )
self._rebuild(newLen, newItems)
def __setitem__(self, index, val):
"Set the item(s) at the specified index/slice."
if isinstance(index, slice):
self._set_slice(index, val)
else:
index = self._checkindex(index)
self._check_allowed((val,))
self._set_single(index, val)
def __iter__(self):
"Iterate over the items in the list"
for i in xrange(len(self)):
yield self[i]
### Special methods for arithmetic operations ###
def __add__(self, other):
'add another list-like object'
return self.__class__(list(self) + list(other))
def __radd__(self, other):
'add to another list-like object'
return other.__class__(list(other) + list(self))
def __iadd__(self, other):
'add another list-like object to self'
self.extend(list(other))
return self
def __mul__(self, n):
'multiply'
return self.__class__(list(self) * n)
def __rmul__(self, n):
'multiply'
return self.__class__(list(self) * n)
def __imul__(self, n):
'multiply'
if n <= 0:
del self[:]
else:
cache = list(self)
for i in range(n-1):
self.extend(cache)
return self
def __eq__(self, other):
for i in range(len(self)):
try:
c = self[i] == other[i]
except IndexError:
# must be other is shorter
return False
if not c:
return False
return True
def __lt__(self, other):
slen = len(self)
for i in range(slen):
try:
c = self[i] < other[i]
except IndexError:
# must be other is shorter
return False
if c:
return c
return slen < len(other)
### Public list interface Methods ###
## Non-mutating ##
def count(self, val):
"Standard list count method"
count = 0
for i in self:
if val == i: count += 1
return count
def index(self, val):
"Standard list index method"
for i in xrange(0, len(self)):
if self[i] == val: return i
raise ValueError('%s not found in object' % str(val))
## Mutating ##
def append(self, val):
"Standard list append method"
self[len(self):] = [val]
def extend(self, vals):
"Standard list extend method"
self[len(self):] = vals
def insert(self, index, val):
"Standard list insert method"
if not isinstance(index, (int, long)):
raise TypeError("%s is not a legal index" % index)
self[index:index] = [val]
def pop(self, index=-1):
"Standard list pop method"
result = self[index]
del self[index]
return result
def remove(self, val):
"Standard list remove method"
del self[self.index(val)]
def reverse(self):
"Standard list reverse method"
self[:] = self[-1::-1]
def sort(self, cmp=cmp, key=None, reverse=False):
"Standard list sort method"
if key:
temp = [(key(v),v) for v in self]
temp.sort(cmp=cmp, key=lambda x: x[0], reverse=reverse)
self[:] = [v[1] for v in temp]
else:
temp = list(self)
temp.sort(cmp=cmp, reverse=reverse)
self[:] = temp
### Private routines ###
def _rebuild(self, newLen, newItems):
if newLen < self._minlength:
raise ValueError('Must have at least %d items' % self._minlength)
if self._maxlength is not None and newLen > self._maxlength:
raise ValueError('Cannot have more than %d items' % self._maxlength)
self._set_list(newLen, newItems)
def _set_single_rebuild(self, index, value):
self._set_slice(slice(index, index + 1, 1), [value])
def _checkindex(self, index, correct=True):
length = len(self)
if 0 <= index < length:
return index
if correct and -length <= index < 0:
return index + length
raise self._IndexError('invalid index: %s' % str(index))
def _check_allowed(self, items):
if hasattr(self, '_allowed'):
if False in [isinstance(val, self._allowed) for val in items]:
raise TypeError('Invalid type encountered in the arguments.')
def _set_slice(self, index, values):
"Assign values to a slice of the object"
try:
iter(values)
except TypeError:
raise TypeError('can only assign an iterable to a slice')
self._check_allowed(values)
origLen = len(self)
valueList = list(values)
start, stop, step = index.indices(origLen)
# CAREFUL: index.step and step are not the same!
# step will never be None
if index.step is None:
self._assign_simple_slice(start, stop, valueList)
else:
self._assign_extended_slice(start, stop, step, valueList)
def _assign_extended_slice_rebuild(self, start, stop, step, valueList):
'Assign an extended slice by rebuilding entire list'
indexList = range(start, stop, step)
# extended slice, only allow assigning slice of same size
if len(valueList) != len(indexList):
raise ValueError('attempt to assign sequence of size %d '
'to extended slice of size %d'
% (len(valueList), len(indexList)))
# we're not changing the length of the sequence
newLen = len(self)
newVals = dict(zip(indexList, valueList))
def newItems():
for i in xrange(newLen):
if i in newVals:
yield newVals[i]
else:
yield self._get_single_internal(i)
self._rebuild(newLen, newItems())
def _assign_extended_slice(self, start, stop, step, valueList):
'Assign an extended slice by re-assigning individual items'
indexList = range(start, stop, step)
# extended slice, only allow assigning slice of same size
if len(valueList) != len(indexList):
raise ValueError('attempt to assign sequence of size %d '
'to extended slice of size %d'
% (len(valueList), len(indexList)))
for i, val in zip(indexList, valueList):
self._set_single(i, val)
def _assign_simple_slice(self, start, stop, valueList):
'Assign a simple slice; Can assign slice of any length'
origLen = len(self)
stop = max(start, stop)
newLen = origLen - stop + start + len(valueList)
def newItems():
for i in xrange(origLen + 1):
if i == start:
for val in valueList:
yield val
if i < origLen:
if i < start or i >= stop:
yield self._get_single_internal(i)
self._rebuild(newLen, newItems())
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