cell and row

[Fredrik Lundh]

Shi Mu wrote:

>I can not understand the use of "cell" and "row" in the code:
>
> # convert the matrix to a 1D list
> matrix = [[13,2,3,4,5],[0,10,6,0,0],[7,0,0,0,9]]
> items = [cell for row in matrix for cell in row]
> print items

working through the Python tutorial might be a good idea.  here's the section
on list comprehensions:

http://docs.python.org/tut/node7.html#SECTION007140000000000000000

and here's the section on for loops:

http://docs.python.org/tut/node6.html#SECTION006200000000000000000

briefly:

    items = [cell for row in matrix for cell in row]

or, slightly edited for clarity:

    items = [(cell)
        for row in matrix
            for cell in row]

is the same thing as:

    items = []
    for row in matrix:
        for cell in row:
            items.append(cell)

except that it's a bit shorter, and a bit more efficient.

</F>