"""Hourglass, by Al Sweigart al@inventwithpython.com An animation of an hourglass with falling sand. Press Ctrl-C to stop. This code is available at https://nostarch.com/big-book-small-python-programming Tags: large, artistic, bext, simulation""" import random, sys, time try: import bext except ImportError: print('This program requires the bext module, which you') print('can install by following the instructions at') print('https://pypi.org/project/Bext/') sys.exit() # Set up the constants: PAUSE_LENGTH = 0.2 # (!) Try changing this to 0.0 or 1.0. # (!) Try changing this to any number between 0 and 100: WIDE_FALL_CHANCE = 50 SCREEN_WIDTH = 79 SCREEN_HEIGHT = 25 X = 0 # The index of X values in an (x, y) tuple is 0. Y = 1 # The index of Y values in an (x, y) tuple is 1. SAND = chr(9617) WALL = chr(9608) # Set up the walls of the hour glass: HOURGLASS = set() # Has (x, y) tuples for where hourglass walls are. # (!) Try commenting out some HOURGLASS.add() lines to erase walls: for i in range(18, 37): HOURGLASS.add((i, 1)) # Add walls for the top cap of the hourglass. HOURGLASS.add((i, 23)) # Add walls for the bottom cap. for i in range(1, 5): HOURGLASS.add((18, i)) # Add walls for the top left straight wall. HOURGLASS.add((36, i)) # Add walls for the top right straight wall. HOURGLASS.add((18, i + 19)) # Add walls for the bottom left. HOURGLASS.add((36, i + 19)) # Add walls for the bottom right. for i in range(8): HOURGLASS.add((19 + i, 5 + i)) # Add the top left slanted wall. HOURGLASS.add((35 - i, 5 + i)) # Add the top right slanted wall. HOURGLASS.add((25 - i, 13 + i)) # Add the bottom left slanted wall. HOURGLASS.add((29 + i, 13 + i)) # Add the bottom right slanted wall. # Set up the initial sand at the top of the hourglass: INITIAL_SAND = set() for y in range(8): for x in range(19 + y, 36 - y): INITIAL_SAND.add((x, y + 4)) def main(): bext.fg('yellow') bext.clear() # Draw the quit message: bext.goto(0, 0) print('Ctrl-C to quit.', end='') # Display the walls of the hourglass: for wall in HOURGLASS: bext.goto(wall[X], wall[Y]) print(WALL, end='') while True: # Main program loop. allSand = list(INITIAL_SAND) # Draw the initial sand: for sand in allSand: bext.goto(sand[X], sand[Y]) print(SAND, end='') runHourglassSimulation(allSand) def runHourglassSimulation(allSand): """Keep running the sand falling simulation until the sand stops moving.""" while True: # Keep looping until sand has run out. random.shuffle(allSand) # Random order of grain simulation. sandMovedOnThisStep = False for i, sand in enumerate(allSand): if sand[Y] == SCREEN_HEIGHT - 1: # Sand is on the very bottom, so it won't move: continue # If nothing is under this sand, move it down: noSandBelow = (sand[X], sand[Y] + 1) not in allSand noWallBelow = (sand[X], sand[Y] + 1) not in HOURGLASS canFallDown = noSandBelow and noWallBelow if canFallDown: # Draw the sand in its new position down one space: bext.goto(sand[X], sand[Y]) print(' ', end='') # Clear the old position. bext.goto(sand[X], sand[Y] + 1) print(SAND, end='') # Set the sand in its new position down one space: allSand[i] = (sand[X], sand[Y] + 1) sandMovedOnThisStep = True else: # Check if the sand can fall to the left: belowLeft = (sand[X] - 1, sand[Y] + 1) noSandBelowLeft = belowLeft not in allSand noWallBelowLeft = belowLeft not in HOURGLASS left = (sand[X] - 1, sand[Y]) noWallLeft = left not in HOURGLASS notOnLeftEdge = sand[X] > 0 canFallLeft = (noSandBelowLeft and noWallBelowLeft and noWallLeft and notOnLeftEdge) # Check if the sand can fall to the right: belowRight = (sand[X] + 1, sand[Y] + 1) noSandBelowRight = belowRight not in allSand noWallBelowRight = belowRight not in HOURGLASS right = (sand[X] + 1, sand[Y]) noWallRight = right not in HOURGLASS notOnRightEdge = sand[X] < SCREEN_WIDTH - 1 canFallRight = (noSandBelowRight and noWallBelowRight and noWallRight and notOnRightEdge) # Set the falling direction: fallingDirection = None if canFallLeft and not canFallRight: fallingDirection = -1 # Set the sand to fall left. elif not canFallLeft and canFallRight: fallingDirection = 1 # Set the sand to fall right. elif canFallLeft and canFallRight: # Both are possible, so randomly set it: fallingDirection = random.choice((-1, 1)) # Check if the sand can "far" fall two spaces to # the left or right instead of just one space: if random.random() * 100 <= WIDE_FALL_CHANCE: belowTwoLeft = (sand[X] - 2, sand[Y] + 1) noSandBelowTwoLeft = belowTwoLeft not in allSand noWallBelowTwoLeft = belowTwoLeft not in HOURGLASS notOnSecondToLeftEdge = sand[X] > 1 canFallTwoLeft = (canFallLeft and noSandBelowTwoLeft and noWallBelowTwoLeft and notOnSecondToLeftEdge) belowTwoRight = (sand[X] + 2, sand[Y] + 1) noSandBelowTwoRight = belowTwoRight not in allSand noWallBelowTwoRight = belowTwoRight not in HOURGLASS notOnSecondToRightEdge = sand[X] < SCREEN_WIDTH - 2 canFallTwoRight = (canFallRight and noSandBelowTwoRight and noWallBelowTwoRight and notOnSecondToRightEdge) if canFallTwoLeft and not canFallTwoRight: fallingDirection = -2 elif not canFallTwoLeft and canFallTwoRight: fallingDirection = 2 elif canFallTwoLeft and canFallTwoRight: fallingDirection = random.choice((-2, 2)) if fallingDirection == None: # This sand can't fall, so move on. continue # Draw the sand in its new position: bext.goto(sand[X], sand[Y]) print(' ', end='') # Erase old sand. bext.goto(sand[X] + fallingDirection, sand[Y] + 1) print(SAND, end='') # Draw new sand. # Move the grain of sand to its new position: allSand[i] = (sand[X] + fallingDirection, sand[Y] + 1) sandMovedOnThisStep = True sys.stdout.flush() # (Required for bext-using programs.) time.sleep(PAUSE_LENGTH) # Pause after this # If no sand has moved on this step, reset the hourglass: if not sandMovedOnThisStep: time.sleep(2) # Erase all of the sand: for sand in allSand: bext.goto(sand[X], sand[Y]) print(' ', end='') break # Break out of main simulation loop. # If this program was run (instead of imported), run the game: if __name__ == '__main__': try: main() except KeyboardInterrupt: sys.exit() # When Ctrl-C is pressed, end the program.