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```class ShiftMatrix(object):
""" An NxN matrix generated by shifting the zeroth row left or right.
Only the zeroth row is stored in memory, the rest is generated. This
cuts memory usage from NxN to a single N.

>>> shift_matrix = ShiftMatrix([1, 2, 3, 4])
>>> print shift_matrix
[1, 2, 3, 4]
[4, 1, 2, 3]
[3, 4, 1, 2]
[2, 3, 4, 1]

>>> shift_matrix = ShiftMatrix([1, 2, 3, 4])
>>> print len(shift_matrix)
16

The class works with any iterable, for example a string:
>>> shift_matrix = ShiftMatrix('Test', shift='left')
>>> print shift_matrix[1]
estT

>>> shift_matrix = ShiftMatrix('Test', shift='left')
>>> print shift_matrix[1][2]
t
"""

def __init__(self, data=None, shift='right'):
if shift in ['right','left']:
self.shift = shift
else:
raise ValueError("Shift direction must be 'right' or 'left'.")
if not data:
self.data = list()
else:
try:
iter(data)
except TypeError, e:
raise TypeError("Object is not iterable.")
self.data = data

def __getitem__(self, index):
if index > len(self.data) - 1:
raise IndexError("Object has no index %d." % index)
if self.shift == 'right':
return self.data[-index % len(self.data):] + self.data[:-index]
if self.shift == 'left':
return self.data[index:] + self.data[:index % len(self.data)]

def __len__(self):
return len(self.data)

def __str__(self):
return "\n".join(str(row) for row in self.__iter__())

def __iter__(self):
for row_index in range(len(self.data)):
yield self.__getitem__(row_index)

if __name__ == "__main__":
shift_matrix = ShiftMatrix([1,2,3],shift='left')
for row in shift_matrix:
print row
```

#### Diff to Previous Revision

```--- revision 6 2012-06-04 20:44:37
+++ revision 7 2012-06-05 12:38:36
@@ -4,12 +4,17 @@
cuts memory usage from NxN to a single N.

>>> shift_matrix = ShiftMatrix([1, 2, 3, 4])
-    >>> for i in range(len(shift_matrix)): print shift_matrix[i]
+    >>> print shift_matrix
[1, 2, 3, 4]
[4, 1, 2, 3]
[3, 4, 1, 2]
[2, 3, 4, 1]

+    >>> shift_matrix = ShiftMatrix([1, 2, 3, 4])
+    >>> print len(shift_matrix)
+    16
+
+    The class works with any iterable, for example a string:
>>> shift_matrix = ShiftMatrix('Test', shift='left')
>>> print shift_matrix[1]
estT
@@ -27,6 +32,10 @@
if not data:
self.data = list()
else:
+            try:
+                iter(data)
+            except TypeError, e:
+                raise TypeError("Object is not iterable.")
self.data = data

def __getitem__(self, index):
@@ -40,7 +49,14 @@
def __len__(self):
return len(self.data)

+    def __str__(self):
+        return "\n".join(str(row) for row in self.__iter__())
+
+    def __iter__(self):
+        for row_index in range(len(self.data)):
+            yield self.__getitem__(row_index)
+
if __name__ == "__main__":
-    shift_matrix = ShiftMatrix('Test', shift='left')
-    for i in range(len(shift_matrix)):
-        print shift_matrix[i]
+    shift_matrix = ShiftMatrix([1,2,3],shift='left')
+    for row in shift_matrix:
+        print row
```