Currently I'm having a data structure course using python. In the book, they have included two different classes to implement the 1D array structure and the 2D array.
For 1D array:
import ctypes
class Array:
def __init__(self, size):
assert size > 0, "Array size must be > 0"
self._size = size
PyArrayType = ctypes.py_object * size
self._elements = PyArrayType()
self.clear(None)
def len(self):
return self._size
def getitem(self, index):
assert index >= 0 and index < self.len(), "Array subscript out of range"
return self._elements[index]
def setitem(self, index, value):
assert 0 <= index < self.len(), "Array subscript out of range"
self._elements[index] = value
def clear(self, value):
for i in range(self.len()):
self._elements[i] = value
def iter(self):
return ArrayIterator(self._elements )
class ArrayIterator:
def __init__(self, theArray):
self._arrayRef = theArray
self._curNdx = 0
def __iter__(self):
return self
def __next__(self):
if self._curNdx < len(self._arrayRef):
entry = self._arrayRef[self._curNdx]
self._curNdx += 1
return entry
else:
raise StopIteration
class Array2D :
def __init__( self, numRows, numCols ):
self._theRows = Array( numRows )
for i in range( numRows ) :
self._theRows[i] = Array( numCols )
def numRows( self ):
return len( self._theRows )
def numCols( self ):
return len( self._theRows[0] )
def clear( self, value ):
for row in range( self.numRows() ):
row.clear( value )
def __getitem__( self, ndxTuple ):
assert len(ndxTuple) == 2, "Invalid number of array subscripts."
row = ndxTuple[0]
col = ndxTuple[1]
assert row >= 0 and row < self.numRows() \
and col >= 0 and col < self.numCols(), \
"Array subscript out of range."
the1dArray = self._theRows[row]
return the1dArray[col]
def __setitem__( self, ndxTuple, value ):
assert len(ndxTuple) == 2, "Invalid number of array subscripts."
row = ndxTuple[0]
col = ndxTuple[1]
assert row >= 0 and row < self.numRows() \
and col >= 0 and col < self.numCols(), \
"Array subscript out of range."
the1dArray = self._theRows[row]
the1dArray[col] = value
I use the following code to understand how it works:
arr = Array(5)
arrLen = arr.len()
arr.clear(0)
for i in range (arrLen):
print arr.getitem(i)
print "The length of the array = ",arrLen
print "Enter 5 numbers"
for i in range (arrLen):
#n = raw_input("num = ")
arr.setitem(i,i)
for i in range (arrLen):
print arr.getitem(i)
print"values are ", arr.iter()
However, I didn't know how to call the 2D array to understand how it works.
ArrMulti = Array2D(3, 4)
and I got the following error:
File "MultiArrayADT.py", line 46, in __init__
self._theRows[i] = Array( numCols )
AttributeError: Array instance has no attribute '__setitem__'
So please can someone tell me how to create a 2D array object.
In your Array
class you should override method __setitem__()
, while you have implemented setitem()
. So try to change a name of the method. That should work. Same with getitem()
.
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