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up vote 16 down vote favorite
3

I have created a multidimensional array in Python like this:

self.cells = np.empty((r,c),dtype=np.object)

Now I want to iterate through all elements of my twodimensional array, and I do not care about the order. How do I achieve this?

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4 Answers 4

up vote 28 down vote accepted

It's clear you're using numpy. With numpy you can just do:

for cell in self.cells.flat:
    do_somethin(cell)
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up vote 13 down vote

If you need to change the values of the individual cells then ndenumerate (in numpy) is your friend. Even if you don't it probably still is!

for index,value in ndenumerate( self.cells ):
    do_something( value )
    self.cells[index] = new_value
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up vote 11 down vote

Just iterate over one dimension, then the other.

for row in self.cells:
    for cell in row:
        do_something(cell)

Of course, with only two dimensions, you can compress this down to a single loop using a list comprehension or generator expression, but that's not very scalable or readable:

for cell in (cell for row in self.cells for cell in row):
    do_something(cell)

If you need to scale this to multiple dimensions and really want a flat list, you can write a flatten function.

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1  
You got it wrong. It should be: for cell in [cell for row in self.cells for cell in row]: do_something(cell) –  xApple Sep 29 '11 at 11:18
    
Wow, this answer is ancient. You're right; will fix. –  Eevee Sep 29 '11 at 17:30
    
Isn't the way he did it fine? It's just a generator expression instead of a list comprehension...am I missing something? O.o –  Shon Freelen Oct 2 '11 at 11:20
    
The 'for's used to be backwards. I edited it since. –  Eevee Oct 4 '11 at 18:22
up vote 4 down vote

How about this:

import itertools
for cell in itertools.chain(*self.cells):
    cell.drawCell(surface, posx, posy)
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itertools.chain.from_iterable(self.cells) –  J.F. Sebastian Oct 18 '09 at 6:27

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