python - Multidimensional Array sets multiple rows/columns -

so having strange problem in python. using code below create plot of places object has been. here code:

def goforward(self, duration):     if (self.towardsx - self.x == 0):         myro.robot.motors(self.speed, self.speed)         myro.wait(abs(duration))         myro.robot.stop()         #get amount of points forward         divisible = (int) (duration / self.scale)         #add them direction         self.towardsy += divisible         tempy = self.y         y in xrange(self.y, divisible + tempy):             if (y % self.scale == 0):                 self.plot[(int) (self.x)][y] = 1         return     #calc slope     slope = (self.towardsy - self.y) / (self.towardsx - self.x)     tempx = self.x     tempy = self.y     #go forward     #get amount of points forward     divisible = duration / self.scale     #add them direction     self.towardsx += divisible     self.towardsy += divisible     xs = []     ys = []     x in xrange(self.x, tempx + divisible):         #find out if plottable point         if (((slope * (x - self.x)) + self.y) % self.scale == 0.0):             xs.append(x)             ys.append((int)((slope * (x - self.x)) + self.y))     #plot points     in xrange(0, len(xs)):         j in xrange(0, len(ys)):             if (self.plot[xs[i]][ys[j]] == 0):                 self.plot[xs[i]][ys[j]] = 1     self.x += divisible     self.y += divisible 

but, when call goforward(2) fills 5 columns ones, instead of few points. example:

[[0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]  [0,0,0,0,1,1,0,0,0,0]] 

based off parameter given goforward(n) creates many columns full of 0s... why behavior happening? code should not produce effect, inexperienced python why happening? in advance

edit

so have changed code plotting points

for in xrange(0, len(xs)):     if (self.plot[xs[i]][ys[i]] == 0):         self.plot[xs[i]][ys[i]] = 1 

which have correct values, still producing strange behavior, , problem lies in code here.

edit 2

when use code:

self.plot[3][3] = 1 

it still produces array of:

[[0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]  [0, 0, 0, 1, 0, 0, 0, 0, 0, 0]] 

so produce grid showing printing self.plot? , saying grid gets initialized 0? self.plot? list of lists , that's it? when print self.plot before running loop print expect (which assume should zeros)?

so if xs , ys points should 1 simplify code using 1 list of plottable points:

plottable_points = [] # loop     plottable_points.append( (x, int((slope * (x - self.x)) + self.y)) )  x, y in plottable_points:     self.plot[x][y] = 1 

i'm not sure how self.plot being initialized or used, if print things before , after each step should able figure out logic wrong.

edit 1: little python tip:

for x, y in zip(xs, ys):     self.plot[x][y] = 1 

does same thing first code example does, variables.

edit 2:

the problem how initializing self.plot. when repeat list that, outer list becomes list of pointers...all pointing same object (in case list). when self.plot[3][3] = 1, setting column in each row. try initializing self.plot (there may better way this, i'm tired):

self.plot = [] col in range(height * multiplyby):     self.plot.append([0] * width * multiplyby)  # or: self.plot = [ [0] * width * multiply col in range(height * multiplyby) ]