title: What does [:, :] mean on NumPy arrays
body: <p>Sorry for the stupid question.
  I'm programming on PHP but found some nice code on Python and want to "recreate" it on PHP.
  But I'm quite frustrated about the line</p>
  
  <pre><code>self.h = -0.1    
  self.activity = numpy.zeros((512, 512)) + self.h
  self.activity[:, :] = self.h
  </code></pre>
  
  <p>But I don't understand what does </p>
  
  <pre><code>[:, :]
  </code></pre>
  
  <p>mean.</p>
  
  <p>Besides I wasn't able to "Google It".</p>
  
  <p>Full code</p>
  
  <pre><code>import math
  import numpy
  import pygame
  from scipy.misc import imsave
  from scipy.ndimage.filters import gaussian_filter
  
  
  class AmariModel(object):
  
      def __init__(self, size):
          self.h = -0.1
          self.k = 0.05
          self.K = 0.125
          self.m = 0.025
          self.M = 0.065
  
          self.stimulus = -self.h * numpy.random.random(size)
          self.activity = numpy.zeros(size) + self.h
          self.excitement = numpy.zeros(size)
          self.inhibition = numpy.zeros(size)
  
      def stimulate(self):
          self.activity[:, :] = self.activity &gt; 0
  
          sigma = 1 / math.sqrt(2 * self.k)
          gaussian_filter(self.activity, sigma, 0, self.excitement, "wrap")
          self.excitement *= self.K * math.pi / self.k
  
          sigma = 1 / math.sqrt(2 * self.m)
          gaussian_filter(self.activity, sigma, 0, self.inhibition, "wrap")
          self.inhibition *= self.M * math.pi / self.m
  
          self.activity[:, :] = self.h
          self.activity[:, :] += self.excitement
          self.activity[:, :] -= self.inhibition
          self.activity[:, :] += self.stimulus
  
  
  class AmariMazeGenerator(object):
  
      def __init__(self, size):
          self.model = AmariModel(size)
  
          pygame.init()
          self.display = pygame.display.set_mode(size, 0)
          pygame.display.set_caption("Amari Maze Generator")
  
      def run(self):
          pixels = pygame.surfarray.pixels3d(self.display)
  
          index = 0
          running = True
          while running:
              self.model.stimulate()
  
              pixels[:, :, :] = (255 * (self.model.activity &gt; 0))[:, :, None]
              pygame.display.flip()
  
              for event in pygame.event.get():
                  if event.type == pygame.QUIT:
                      running = False
                  elif event.type == pygame.KEYDOWN:
                      if event.key == pygame.K_ESCAPE:
                          running = False
                      elif event.key == pygame.K_s:
                          imsave("{0:04d}.png".format(index), pixels[:, :, 0])
                          index = index + 1
                  elif event.type == pygame.MOUSEBUTTONDOWN:
                      position = pygame.mouse.get_pos()
                      self.model.activity[position] = 1
  
          pygame.quit()
  
  
  def main():
      generator = AmariMazeGenerator((512, 512))
      generator.run()
  
  
  if __name__ == "__main__":
      main()
  </code></pre>