Multi-dimensional Array Implementation in Python 3.2 besides with the coincidence of C#

Download multiray.py.zip for Python 3.x[^]

Download multiray.cs.zip (updated 05.08.2011)[^]

Introduction

You can easily make use of Multiray class for issues regarding multidimensional arrays. Now you can download C# version of multiray completely with the same structure as python version.

Using the Code

The usage is simple:

1. Initialize Multiray object with predefined dimensions:
   Python
   

   a = Multiray(2, 5, 20, 6);
   

   C#
   

   using multiray;
   MultiRay a = new MultiRay(2, 5, 20, 6);
   

2. Assign your data values to multi-index specified cells:
   Python
   

   #a[1, 4, 21, 1] will assert an overflow.
   a[1, 2, 18, 5] = "Any Object";
   

   C#
   

   //a[1, 4, 21, 1] will raise an exception.
   a[1, 2, 18, 5] = "Any Object";
   

3. Looping is somewhat like jagged arrays. Use GetLength(d) for any dimension with index d.
   Python
   

   for i in range(a.GetLength(0)):
     for j in range(a.GetLength(1)):
       for k in range(a.GetLength(2)):
         for l in range(a.GetLength(3)):
           #do anything you want with
           #a[i, j, k, l];
           print("a[{1:3}]={0}".format(a[i, j, k, l], a.Position));
   

   C#
   

   for (int i = 0; i < a.GetLength(0); i++)
       for (int j = 0; j < a.GetLength(1); j++)
           for (int k = 0; k < a.GetLength(2); k++)
               for (int l = 0; l < a.GetLength(3); l++)
               {
                   a[i, j, k, l] = "Hello World";
                   Console.WriteLine("a[{0},{1},{2},{3}] = {4}"
                       , i, j, k, l, a[i, j, k, l]);
               }
   

_EvaluateIndex gets real index of given indexes-tuple with this principle:

• if a is a (I x J x K) three dimensional array; let a[i][j][k] nth item in a array. In Multiray implementation, n is evaluated by _EvaluateIndex() method call.
• for D = 3, n is thus:

n = i*J*K + j*K + k;

• for D = 4(I x J x K x T :: i, j, k, t) n is thus:

n = i*J*K*T + j*K*T + k*K + t;

• We multiply the first key with J, K and T; second key with K and T; third with T and fourth with 1
• So we need to multiply first index with keys[1]*keys[2]*keys[3] second key with keys[2]*keys[3] and so on...
• _EvaluateIndex definitely do this:
  Python
  

  def _EvaluateIndex(self, keys, k):
      dLen = len(self.Dimensions);
      #attention!
      #check recursive deadline:
      if k == dLen: return keys[-1];
      t = 1; #accumulator
      #multiply t with the given dimensions k to dLen
      for i in range(k, dLen):
        t *= self.Dimensions[i]
      t *= keys[k - 1];
      return t + self._EvaluateIndex(keys, k=k+1);

  C#
  

  private int _EvaluateIndex(int[] keyTuple, int k)
  {
      int dLen = this.Dimensions.Length;
      if (k == dLen)
          return keyTuple[keyTuple.Length - 1];
      int t = 1;
      for (int i = k; i < dLen; i++)
      {
          t *= this.Dimensions[i];
      }
      t *= keyTuple[k - 1];
      return t + this._EvaluateIndex(keyTuple, k + 1);
  }
  

How is it possible using Multiray object with an indexer?

• Solution is implementing __getitem__ and __setitem__:
  Python
  

    
  def __getitem__(self, keyTuple):
      keys = self._CheckKeys(keyTuple);
      self.Position = self._EvaluateIndex(keys, k=1);
      return self._Arr2D[self.Position];

• self._CheckKeys makes checks and conversion of minus indexes(a[2,3,-2]); then self.Position is evaluated and is given as index to the self._Arr2D array.
  Python
  

    
  def __setitem__(self, keyTuple, item):
      keys = self._CheckKeys(keyTuple);
      self.Position = self._EvaluateIndex(keys, k=1);
      self._Arr2D[self.Position] = item

  C#
  

  public object this[params int[] keyTuple]
  {
      get
      {
          int[] keys = this._CheckKeys(keyTuple);
          this.Position = this._EvaluateIndex(keys, 1);
          return this._Arr2D[this.Position];
      }
      set
      {
          int[] keys = this._CheckKeys(keyTuple);
          this.Position = this._EvaluateIndex(keys, 1);
          this._Arr2D[this.Position] = value;
      }
  }
  

• Again self._CheckKeys() makes checks and manipulations:
  Python
  

  def _CheckKeys(self, keyTuple):
      assert(len(keyTuple) == len(self.Dimensions));
      keyList = list(keyTuple);
      limit = len(keyList);
      for i in range(limit):
        assert(keyList[i] < self.Dimensions[i] \
               and keyList[i] >= -self.Dimensions[i]);
        #for minus indexes:
        #like a[1,-2]
        if keyList[i] < 0:
          keyList[i] += self.Dimensions[i];
      return keyList;
  

  C#
  

  private int[] _CheckKeys(int[] keyTuple)
  {
      Debug.Assert(keyTuple.Length == this.Dimensions.Length);
      int limit = keyTuple.Length;
      int[] keyList = new int[limit];
      for (int i = 0; i < limit; i++)
      {
          Debug.Assert(keyList[i] < this.Dimensions[i]
              && keyList[i] >= -this.Dimensions[i]);
          keyList[i] = keyTuple[i];
          //for negative indexes
          //like a[1,-2]
          if (keyList[i] < 0)
              keyList[i] += this.Dimensions[i];
      }
      return keyList;
  }
  

Last word

• I found out that "," delimeted indexes are passed in tuples. So when I use a[1,2,3] __getitem__ takes (1,2,3) tuple.
• So positional arguments not needed for now.

Points of Interest

I suffered from invalid mathematical evaluations. By the help of induction, I could eventually implement the right way of function.

History

The previous version lacked c sharp in advance.