How to get index of item

Question

I am trying to get a index of items to the left, right, bottom, and top of a binary integer in a 4x4 grid. With what I am doing now doesn't seem to be getting the correct index of a value.

        if self.data[index] == 1:
            self.data[index] = 0
                if self.data.index(self.data[index]) - 1 >= 0:
                    print("Left toggled")
                    if self.data[index - 1] == 1:
                        self.data[index - 1] = 0
                    else:
                        self.data[index - 1] = 1

As of now I am trying with the bit array of 010011100100 which is returning a -1 if index = 5 in the above code example when it should be returning 4 as 5-1=4.

I assume my if statement if self.data.index(self.data[index]) - 1 >= 0: is wrong, but I am unsure of the syntax of what I am trying to accompish.

Answer 1

Lets step through your code and see what happens...

#We'll fake these in so the code makes sence...
#self.data must be an array as you can't reassign as you are doing later
self.data = list("010011100100")
index = 5

if self.data[index] == 1:      # Triggered, as self.data[:5] is  "010011"
    self.data[index] = 0       # AHA self.data is now changed to "010010..."!!!
        if self.data.index(self.data[index]) - 1 >= 0:
           #Trimmed

In the second last line you are getting self.data[index] which is now 0 as we changed it the line before.

But also, remember that Array.index() returns the first instance of that item in the array. So self.data.index(0) returns the first instance of 0 , which is the first or more precicely, zeroth element. Thus is self.data.index(0) gives 0 and 0-1 is... -1 .

As for what your code should be, that is a tougher answer.

I think your conditional may just be:

width  = 4 # For a 4x4 grid, defined much earlier.
height = 4 # For a 4x4 grid, defined much earlier.

...

if index%width == 0:
    print "we are on the left edge"
if index%width == width - 1:
    print "we are on the right edge"
if index%height == 0:
    print "we are on the top edge"
if index%height == height - 1:
    print "we are on the bottom edge"