Is there a Python module/recipe (not numpy) for 2d arrays for small games

Question

I am writing some small games in Python with Pygame & Pyglet as hobby projects.

A class for 2D array would be very handy. I use py2exe to send the games to relatives/friends and numpy is just too big and most of it's features are unnecessary for my requirements.

Could you suggest a Python module/recipe I could use for this.

-- Chirag

[Edit]: List of lists would be usable as mentioned below by MatrixFrog and zvoase. But it is pretty primitive. A class with methods to insert/delete rows and columns as well as to rotate/flip the array would make it very easy and reusable too. dicts are good for sparse arrays only.

Thank you for your ideas.

Answer 1

How about using a defaultdict?

>>> import collections
>>> Matrix = lambda: collections.defaultdict(int)
>>> m = Matrix()
>>> m[3,2] = 6
>>> print m[3,4]   # deliberate typo :-)
0
>>> m[3,2] += 4
>>> print m[3,2]
10
>>> print m
defaultdict(<type 'int'>, {(3, 2): 10, (3, 4): 0})

As the underlying dict uses tuples as keys, this supports 1D, 2D, 3D, ... matrices.

Answer 2

The simplest approach would just be to use nested lists:

>>> matrix = [[0] * num_cols] * num_rows
>>> matrix[i][j] = 'value' # row i, column j, value 'value'
>>> print repr(matrix[i][j])
'value'

Alternatively, if you're going to be dealing with sparse matrices (ie matrices with a lot of empty or zero values), it might be more efficient to use nested dictionaries. In this case, you could implement setter and getter functions which will operate on a matrix, like so:

def get_element(mat, i, j, default=None):
    # This will also set the accessed row to a dictionary.
    row = mat.setdefault(i, {})
    return row.setdefault(j, default)

def set_element(mat, i, j, value):
    row = mat.setdefault(i, {})
    row[j] = value

And then you would use them like this:

>>> matrix = {}
>>> set_element(matrix, 2, 3, 'value') # row 2, column 3, value 'value'
>>> print matrix
{2: {3: 'value'}}
>>> print repr(get_element(matrix, 2, 3))
'value'

If you wanted, you could implement a Matrix class which implemented these methods, but that might be overkill:

class Matrix(object):
    def __init__(self, initmat=None, default=0):
        if initmat is None: initmat = {}
        self._mat = initmat
        self._default = default
    def __getitem__(self, pos):
        i, j = pos
        return self._mat.setdefault(i, {}).setdefault(j, self._default)  
    def __setitem__(self, pos, value):
        i, j = pos
        self._mat.setdefault(i, {})[j] = value
    def __repr__(self):
        return 'Matrix(%r, %r)' % (self._mat, self._default)

>>> m = Matrix()
>>> m[2,3] = 'value'
>>> print m[2,3]
'value'
>>> m
Matrix({2: {3: 'value'}}, 0)

Answer 3

也许pyeuclid符合您的需求 - （过时但可用）格式化的文档在这里 ，ReST格式的最新文档在pyeuclid源文本文件中（要做自己的ReST文本格式，使用docutils ）。

Answer 4

I wrote the class. Don't know if it is a good or redundant but... Posted it here http://bitbucket.org/pieceofpeace/container2d/