Indexing a list using the values in a tuple in python

Question

I have a list of tuples:
indices = [ (0,1) , (1,2) , (5,9) , ...] each tuple represent an index to be used with a list of lists representing a grid.

what I am doing to extract the actual values corresponding to the indices is:

for index in indices:
    x = grid [index[0]] [index[1]] # get the value and move on

Is there any better way to achieve this ? maybe something more "pythonic :D "

Thanks

Without knowing your application, the use of list of lists to create a grid sounds like you are missing numpy arrays. With an array you could, for example, use grid[zip(*indices)] and get all points you have in the indices, or just point by the tuples, e.g. grid[(5,9)]. Whether or not this is worth loading numpy depends on your application. If you do any maths, it is usually worth it. — DrV
– DrV, Commented Jun 15, 2014 at 20:56
:) I know the feeling... However, as Cyber has shown below, there are a couple of alternatives depending on what you really want to do. Oh, and there is still the mickeymouse solution with you using a single list and doing the row/column arithmetics yourself. That may be the fastest solution, if you want to have speed. (Pythonic? Certainly not.) — DrV
– DrV, Commented Jun 15, 2014 at 21:29

Cory Kramer · Accepted Answer · 2014-06-15 20:44:53Z

1

You could use a list comp

[grid[x][y] for x, y in indices]

Or if you still need to do stuff once you get the value:

for x,y in indices:
    i = grid[x][y]
    # do stuff with i

edited Jun 15, 2014 at 20:44

answered Jun 15, 2014 at 20:42

Cory Kramer

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