Question

I have a 2D list where each “row” has an index, name, and a path like [(1L, "bar", "foo/bar"), (2L, "app", "some/app"),] etc. I am trying to retrieve a “row” from this 2D list given and index. For example, an index of 1 should return (1L, "bar", "foo/bar"). I know I can loop through my whole list and compare the index until I find the object like so:

my_index = 1    
for row in my_list:
    if (row[0] == my_index)
        return row
return False

I was wondering if there is a cleaner/nicer way to do this in python, since I am new to python. I know there is an index method for a list that returns the index from a list but I’m not sure how I can use that with a 2D list. Thanks in advance! Oh and also, it can be assumed that there will only be one instance of each object (i.e: no duplicates)

Answer 1

It looks like you would be better off using a dictionary instead of a list, so your data would look like this:

my_dict = {1L: (1L, "bar", "foo/bar"),
           2L: (2L, "app", "some/app")}

This allows you to efficiently access each element by index:

>>> my_dict[1]
(1L, 'bar', 'foo/bar')

Here is how you could create the dictionary from the list:

my_dict = {row[0]: row for row in my_list}

Or on Python 2.6 and below:

my_dict = dict((row[0], row) for row in my_list)