Python program errors -

i'm writing program needs find pairs of initial conditions (x0,y0) x goes extinct first , plot them.the equations are:

j=x-y+100 , i=x+y-100

and constraints (0,200) in both x , y directions.

my code looks this:

for x in range (0,201): y in range (0,201):     c=0     i=x     j=y while (x > 0 , y > 0):     i=x-y+100     j=x+y-100     c=c+1 if i==0:     plot(i,j) if c==50:     break 

and error says:

    traceback (most recent call last):                i=x-y+100   file "", line 1, in <module>    file "/tmp/tmpqtzdaj/___code___.py", line 3, in <module>     exec compile(u'for x in range (_sage_const_0 ,_sage_const_201 ):\n    y in range (_sage_const_0 ,_sage_const_201 ):\n        c=_sage_const_0 \n        i=x\n        j=y\n        while (x > _sage_const_0  , y > _sage_const_0 ):\n            i=x-y+_sage_const_100 \n            j=x+y-_sage_const_100 \n            c=c+_sage_const_1 \n        if i==_sage_const_0 :\n            plot([i],[j])\n        if c==_sage_const_50 :\n            break   file "", line 11, in <module>    file "/app/sage/sage-6.1.1/local/lib/python2.7/site-packages/sage/misc/decorators.py", line 692, in wrapper     return func(*args, **kwds)   file "/app/sage/sage-6.1.1/local/lib/python2.7/site-packages/sage/misc/decorators.py", line 537, in wrapper     return func(*args, **options)   file "/app/sage/sage-6.1.1/local/lib/python2.7/site-packages/sage/plot/plot.py", line 1134, in plot     g = _plot(funcs, *args, **kwds)   file "/app/sage/sage-6.1.1/local/lib/python2.7/site-packages/sage/plot/plot.py", line 1236, in _plot     funcs, ranges = setup_for_eval_on_grid(funcs, [xrange], options['plot_points'])   file "/app/sage/sage-6.1.1/local/lib/python2.7/site-packages/sage/plot/misc.py", line 132, in setup_for_eval_on_grid     range_steps = [abs(range[1] - range[0])/(p-1) range, p in zip(ranges, plot_points)] indexerror: list index out of range 

the problem passing integer plot() when expects array.

at point internally, tries length of array , fails because can't take length of integer.

at guess, code should like

max_reps = 50  good_pts = []  x in range (0,201):     y in range (0,201):         c in range(max_reps):             x, y = x - y + 100, x + y - 100              if y <= 0:                 break             elif x <= 0:                 good_pts.append((x, y))                 break 

then plot (x, y) points in good_pts.