[Tutor] Basic Question

[Peter Otten]

On 10/09/2021 10:21, Alan Gauld via Tutor wrote:
> On 09/09/2021 22:58, Osmaan Mysorewala via Tutor wrote:
> 
>> One more question. In my get_neighbors function I use a terrible
>> if-statement spam, how would I go about replacing that?
> I assume you mean this section:
> 
> def get_neighbors(a, b):
>      neighbors = 0
>      if old_arr[a + 1][b] == 1:
>          neighbors = neighbors + 1
>      if old_arr[a - 1][b] == 1:
>          neighbors = neighbors + 1

> I don't think its terrible but it can be tidied up provided
> the values you store are zero and one. Then you can miss
> out the if statements and replace them with addition:
> 
>      neighbors = neighbors + old_arr[a + 1][b] # or using +=...
>      neighbours += old_arr[a - 1][b]
>      neighbours += old_arr[a][b+1]

Osmaan, while I agree with Alan that the if statements aren't "terrible" 
I'd like to suggest that you revisit your failed attempt to use loops:

>     for na in range(a - 1, a + 1):
>         for nb in range(b - 1, b + 1):
>             if (na != a and nb != b) and old_arr[na][nb]:
>                 neighbors = neighbors + 1

This should work once

(1) you get the range() calls right

hint: Python's ranges are "half open", i. e. they do not include the 
last value:

 >>> list(range(3))
[0, 1, 2]
 >>> a = 42
 >>> list(range(a-1, a+1))
[41, 42]

(2) in the first condition of the if statement you only exclude the cell 
(a, b)

hint: start with an expression that's true for (a, b), then negate that with

if not (...to be done...) and old_arr[na][nb]:
     ...