new tasks

Task/Forest_fire/Python/forest_fire.py

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+'''
+Forest-Fire Cellular automation
+ See: http://en.wikipedia.org/wiki/Forest-fire_model
+'''
+
+L = 15
+# d = 2 # Fixed
+initial_trees = 0.55
+p = 0.01
+f = 0.001
+
+try:
+    raw_input
+except:
+    raw_input = input
+
+import random
+
+
+tree, burning, space = 'TB.'
+hood = ((-1,-1), (-1,0), (-1,1),
+        (0,-1),          (0, 1),
+        (1,-1),  (1,0),  (1,1))
+
+def initialise():
+    grid = {(x,y): (tree if random.random()<= initial_trees else space)
+            for x in range(L)
+            for y in range(L) }
+    return grid
+
+def gprint(grid):
+    txt = '\n'.join(''.join(grid[(x,y)] for x in range(L))
+                    for y in range(L))
+    print(txt)
+
+def quickprint(grid):
+    t = b = 0
+    ll = L * L
+    for x in range(L):
+        for y in range(L):
+            if grid[(x,y)] in (tree, burning):
+                t += 1
+                if grid[(x,y)] == burning:
+                    b += 1
+    print(('Of %6i cells, %6i are trees of which %6i are currently burning.'
+          + ' (%6.3f%%, %6.3f%%)')
+          % (ll, t, b, 100. * t / ll, 100. * b / ll))
+
+
+def gnew(grid):
+    newgrid = {}
+    for x in range(L):
+        for y in range(L):
+            if grid[(x,y)] == burning:
+                newgrid[(x,y)] = space
+            elif grid[(x,y)] == space:
+                newgrid[(x,y)] = tree if random.random()<= p else space
+            elif grid[(x,y)] == tree:
+                newgrid[(x,y)] = (burning
+                                   if any(grid.get((x+dx,y+dy),space) == burning
+                                            for dx,dy in hood)
+                                        or random.random()<= f
+                                   else tree)
+    return newgrid
+
+if __name__ == '__main__':
+    grid = initialise()
+    iter = 0
+    while True:
+        quickprint(grid)
+        inp = raw_input('Print/Quit/<int>/<return> %6i: ' % iter).lower().strip()
+        if inp:
+            if inp[0] == 'p':
+                gprint(grid)
+            elif inp.isdigit():
+                for i in range(int(inp)):
+                    iter +=1
+                    grid = gnew(grid)
+                    quickprint(grid)
+            elif inp[0] == 'q':
+                break
+        grid = gnew(grid)
+        iter +=1