Memory Error while simulating matrix

[Skip Montanaro]

    slick> When i execute the code(part of an algorithm code) given below, i
    slick> get a MemoryError.

    row = []                # list 
    row = [0] * 1000000     # each row contains million columns 
    matrix =[]              # contains a collection of rows  

    for i in range(1000):   # creating a matix of 1000 rows each 
      matrix.append(row[:]) # having a million  columns

You are trying to create 1,000 lists, each with 1,000,000 elements, or 10**9
4-byte object pointers, so at minimum you will be chewing 4GB of virtual
memory, probably much more once your matrix becomes a bit less uniform.  To
keep from getting a MemoryError you should have at least that much swap
space.  Actually much more.  Integer overhead is 12 bytes per object.
(Float overhead is 16 bytes per object.)  Assuming most of the elements of
your matrix are not recycled integers between -1 and 100, your memory
consumption will be closer to 20GB than 4GB.

Obviously, you can use the array module or NumPy.  Both of those are going
to push the memory consumption closer to the 4GB end of things.

-- 
Skip Montanaro (skip at pobox.com - http://www.mojam.com/)