Help doing it the "python way"

[Terry Reedy]

On 5/24/2012 4:53 PM, Duncan Booth wrote:
> Scott Siegler<scott.siegler at gmail.com>  wrote:
>
>> Hello,
>>
>> I am an experienced programmer but a beginner to python.  As such, I
>> can figure out a way to code most algorithms using more "C" style
>> syntax.

Hi, welcome to Python. I came here from C also.

>> I am doing something now that I am sure is a more python way but i
>> can't quite get it right.  I was hoping someone might help.
>>
>> So I have a list of grid coordinates (x, y).  From that list, I want
>> to create a new list that for each coordinate, I add the coordinate
>> just above and just below (x,y+1) and (x,y-1)

The Python way, especially the Python 3 way, is to not make the new 
sequence into a concrete list unless you actually need a list to append 
or sort or otherwise mutate. In many use cases, that is not necessary.

>> right now I am using a for loop to go through all the coordinates and
>> then separate append statements to add the top and bottom.
>>
>> is there a way to do something like: [(x,y-1), (x,y+1) for zzz in
>> coord_list] or something along those lines?

> def vertical_neighbours(coords):
>      for x, y in coords:
>          yield x, y-1
>          yield x, y+1
>
> new_coords = list(vertical_neighbours(coords))

-- 
Terry Jan Reedy