Hacktoberfest 2020: Conway's Game of Life (#3070)

* Created conways_game_of_life.py

* Added new_generation(list[int[int]]) -> list[list[int]]

* Added glider example

* Added comments and shortened glider example

* Fixed index out of bounds error

* Added test

* Added blinker example

* Added ability to generate images

* Moved image generating code into a separate function

* Added comments

* Comment

* Reformatted file

* Formatting

* Removed glider test

* Update cellular_automata/conways_game_of_life.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

* Update conways_game_of_life.py

* Update conways_game_of_life.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

cellular_automata/conways_game_of_life.py

@@ -0,0 +1,100 @@
+"""
+Conway's Game of Life implemented in Python.
+https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life
+"""
+
+from __future__ import annotations
+
+from typing import List
+
+from PIL import Image
+
+# Define glider example
+GLIDER = [
+    [0, 1, 0, 0, 0, 0, 0, 0],
+    [0, 0, 1, 0, 0, 0, 0, 0],
+    [1, 1, 1, 0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0, 0, 0, 0],
+]
+
+# Define blinker example
+BLINKER = [[0, 1, 0], [0, 1, 0], [0, 1, 0]]
+
+
+def new_generation(cells: List[List[int]]) -> List[List[int]]:
+    """
+    Generates the next generation for a given state of Conway's Game of Life.
+    >>> new_generation(BLINKER)
+    [[0, 0, 0], [1, 1, 1], [0, 0, 0]]
+    """
+    next_generation = []
+    for i in range(len(cells)):
+        next_generation_row = []
+        for j in range(len(cells[i])):
+            # Get the number of live neighbours
+            neighbour_count = 0
+            if i > 0 and j > 0:
+                neighbour_count += cells[i - 1][j - 1]
+            if i > 0:
+                neighbour_count += cells[i - 1][j]
+            if i > 0 and j < len(cells[i]) - 1:
+                neighbour_count += cells[i - 1][j + 1]
+            if j > 0:
+                neighbour_count += cells[i][j - 1]
+            if j < len(cells[i]) - 1:
+                neighbour_count += cells[i][j + 1]
+            if i < len(cells) - 1 and j > 0:
+                neighbour_count += cells[i + 1][j - 1]
+            if i < len(cells) - 1:
+                neighbour_count += cells[i + 1][j]
+            if i < len(cells) - 1 and j < len(cells[i]) - 1:
+                neighbour_count += cells[i + 1][j + 1]
+
+            # Rules of the game of life (excerpt from Wikipedia):
+            # 1. Any live cell with two or three live neighbours survives.
+            # 2. Any dead cell with three live neighbours becomes a live cell.
+            # 3. All other live cells die in the next generation.
+            #    Similarly, all other dead cells stay dead.
+            alive = cells[i][j] == 1
+            if (
+                (alive and 2 <= neighbour_count <= 3)
+                or not alive
+                and neighbour_count == 3
+            ):
+                next_generation_row.append(1)
+            else:
+                next_generation_row.append(0)
+
+        next_generation.append(next_generation_row)
+    return next_generation
+
+
+def generate_images(cells: list[list[int]], frames) -> list[Image.Image]:
+    """
+    Generates a list of images of subsequent Game of Life states.
+    """
+    images = []
+    for _ in range(frames):
+        # Create output image
+        img = Image.new("RGB", (len(cells[0]), len(cells)))
+        pixels = img.load()
+
+        # Save cells to image
+        for x in range(len(cells)):
+            for y in range(len(cells[0])):
+                colour = 255 - cells[y][x] * 255
+                pixels[x, y] = (colour, colour, colour)
+
+        # Save image
+        images.append(img)
+        cells = new_generation(cells)
+    return images
+
+
+if __name__ == "__main__":
+    images = generate_images(GLIDER, 16)
+    images[0].save("out.gif", save_all=True, append_images=images[1:])