Simplify the pyplot animation demo.

anntzer · anntzer · commit c1b6a1c39fdd · 2017-11-24T14:17:51.000-08:00
Focus the pyplot animation demo to just 1) do some simple plotting, 2)
call pause().

Yes, it would be more efficient to reuse the same image.  But if we are
not using the animation module, efficiency is probably the least of our
worries.
diff --git a/examples/animation/animation_demo.py b/examples/animation/animation_demo.py
@@ -1,31 +1,28 @@
 """
-==============
-Animation Demo
-==============
+================
+pyplot animation
+================
 
-Pyplot animation example.
+Generating an animation by calling `~.pyplot.pause` between plotting commands.
 
-The method shown here is only for very simple, low-performance
-use.  For more demanding applications, look at the animation
-module and the examples that use it.
+The method shown here is only suitable for simple, low-performance use.  For
+more demanding applications, look at the :mod:`animation` module and the
+examples that use it.
+
+Note that calling `time.sleep` instead of `~.pyplot.pause` would *not* work.
 """
 
 import matplotlib.pyplot as plt
 import numpy as np
 
-x = np.arange(6)
-y = np.arange(5)
-z = x * y[:, np.newaxis]
+np.random.seed(19680801)
+data = np.random.random((50, 50, 50))
 
-for i in range(5):
-    if i == 0:
-        p = plt.imshow(z)
-        fig = plt.gcf()
-        plt.clim()   # clamp the color limits
-        plt.title("Boring slide show")
-    else:
-        z = z + 2
-        p.set_data(z)
+fig, ax = plt.subplots()
 
-    print("step", i)
-    plt.pause(0.5)
+for i in range(len(data)):
+    ax.cla()
+    ax.imshow(data[i])
+    ax.set_title("frame {}".format(i))
+    # Note that using time.sleep does *not* work here!
+    plt.pause(0.1)
