Python matplotlib - 在Conway的生命游戏中动画期间更新数据

Question

下面的代码使用Python和matplotlib为Conway的生命游戏创建动画。

我不确定为什么要这样做：

grid = newGrid.copy()
mat.set_data(grid)

而不仅仅是：

mat.set_data(newGrid)

如何在没有上述复制的情况下更新与绘图关联的数组？

import numpy as np
import matplotlib.pyplot as plt 
import matplotlib.animation as animation

N = 100
ON = 255
OFF = 0
vals = [ON, OFF]

# populate grid with random on/off - more off than on
grid = np.random.choice(vals, N*N, p=[0.2, 0.8]).reshape(N, N)

def update(data):
  global grid
  newGrid = grid.copy()
  for i in range(N):
    for j in range(N):
      total = (grid[i, (j-1)%N] + grid[i, (j+1)%N] + 
               grid[(i-1)%N, j] + grid[(i+1)%N, j] + 
               grid[(i-1)%N, (j-1)%N] + grid[(i-1)%N, (j+1)%N] + 
               grid[(i+1)%N, (j-1)%N] + grid[(i+1)%N, (j+1)%N])/255

      if grid[i, j]  == ON:
        if (total < 2) or (total > 3):
          newGrid[i, j] = OFF
      else:
        if total == 3:
          newGrid[i, j] = ON

  grid = newGrid.copy()
  mat.set_data(grid)
  return mat 

fig, ax = plt.subplots()
mat = ax.matshow(grid)
ani = animation.FuncAnimation(fig, update, interval=50,
                              save_count=50)
plt.show()

输出似乎是正确的 - 我可以看到滑翔机和其他预期的模式：

Answer 1

mat.set_data()需要newGrid的副本没有特别的原因 - 重要的是全局grid从迭代更新到迭代：

def update(data):
  global grid
  newGrid = grid.copy()

  """
  do your updating. this needs to be done on a copy of 'grid' because you are
  updating element-by-element, and updates to previous rows/columns will
  affect the result at 'grid[i,j]' if you don't use a copy
  """

  # you do need to update the global 'grid' otherwise the simulation will
  # not progress, but there's no need to copy()
  mat.set_data(newGrid)
  grid = newGrid

  # # there's no reason why you couldn't do it in the opposite order
  # grid = newGrid
  # mat.set_data(grid)

  # at least in my version of matplotlib (1.2.1), the animation function must
  # return an iterable containing the updated artists, i.e. 'mat,' or '[mat]',
  # not 'mat'
  return [mat]

此外，在FuncAnimation我建议传递blit=True，这样您就不会在每一帧上重新绘制背景。