python checking if coordinates already exist in list -

this work assignment. working 2d array , far have found path want take through array. there other paths in array , want able go through them cannot reuse paths. array looks like:

0,2,4,1,6,0,0 2,0,0,0,5,0,0 4,0,0,0,5,5,0 1,0,0,0,1,1,0 6,5,0,1,0,5,5 0,0,5,1,5,0,0 0,0,0,0,5,0,0 

my code finding nearby neighbours is:

def check_neighbours(alist, node):         nodes = []         in range(0,2):                 j in range(0,2):                         x = node[0]+i                         y = node[1]+j                         if x>=0 , y>=0 , (i!=0 or j!=0) , alist[x][y]>0:                                 nodes.append([x, y]) 

i appending each visited coordinate x,y list builds full path taken. here example of output:

inside pathing function path taken ['[0, 1]', '[0, 2]', '[0, 3]', '[0, 4]', '[1, 4]', '[2, 4]', '[2, 5]', '[3, 5]', '[4, 5]', '[4, 6]'] 

because of way searching neighbours (having x , y separated) cannot think of way of testing whether or not current coordinate built located inside of list. think code fit in between following 2 lines:

if x>=0 , y>=0 , (i!=0 or j!=0) , alist[x][y]>0:                                     nodes.append([x, y]) 

what about

nodes = [] nodes.append([1,1]) nodes.append([2,2]) nodes.append([3,3])  [1,1] in nodes # true  [1,3] in nodes # false 

i'm not clear on question, may off.

that being said, since, in order added nodes list, has either 1 column right, 1 below, or both, of previous node. , since you're considering nodes right , below (range(0,2)), can never duplicates in list.