Trac #33264: add "x = SR.var('x')" to several animation examples.

The (absence of the) implicitly defined "x" often causes new users some confusion in code that uses "x" for another purpose. Here we make the definition explicit within the examples for sage.plot.animate.py.
sagemath · Feb 3, 2022 · e73cd12 · e73cd12
1 parent 439907f
commit e73cd12
Showing 1 changed file with 21 additions and 7 deletions.
diff --git a/src/sage/plot/animate.py b/src/sage/plot/animate.py
@@ -30,6 +30,7 @@
 
 The sine function::
 
+    sage: x = SR.var("x")
     sage: sines = [plot(c*sin(x), (-2*pi,2*pi), color=Color(c,0,0), ymin=-1, ymax=1) for c in sxrange(0,1,.2)]
     sage: a = animate(sines)
     sage: a         # optional -- ImageMagick
@@ -61,8 +62,7 @@
 
 Animations of 3d objects::
 
-    sage: var('s,t')
-    (s, t)
+    sage: s,t = SR.var("s,t")
     sage: def sphere_and_plane(x):
     ....:     return sphere((0,0,0),1,color='red',opacity=.5)+parametric_plot3d([t,x,s],(s,-1,1),(t,-1,1),color='green',opacity=.7)
     sage: sp = animate([sphere_and_plane(x) for x in sxrange(-1,1,.3)])
@@ -72,7 +72,7 @@
     Graphics3d Object
     sage: sp.show()  # optional -- ImageMagick
 
-    sage: (x,y,z) = var('x,y,z')
+    sage: (x,y,z) = SR.var("x,y,z")
     sage: def frame(t):
     ....:     return implicit_plot3d((x^2 + y^2 + z^2), (x, -2, 2), (y, -2, 2), (z, -2, 2), plot_points=60, contour=[1,3,5], region=lambda x,y,z: x<=t or y>=t or z<=t)
     sage: a = animate([frame(t) for t in srange(.01,1.5,.2)])
@@ -85,7 +85,7 @@
 method :meth:`sage.plot.animate.Animation.make_image`.  This is
 illustrated by the following example::
 
-    sage: t = var('t')
+    sage: t = SR.var("t")
     sage: a = animate((sin(c*pi*t) for c in sxrange(1,2,.2)))
     sage: a.show()  # optional -- ImageMagick
 
@@ -133,7 +133,7 @@ def animate(frames, **kwds):
 
     EXAMPLES::
 
-        sage: t = var('t')
+        sage: t = SR.var("t")
         sage: a = animate((cos(c*pi*t) for c in sxrange(1,2,.2)))
         sage: a.show()  # optional -- ImageMagick
 
@@ -161,6 +161,7 @@ class Animation(WithEqualityById, SageObject):
 
     EXAMPLES::
 
+        sage: x = SR.var("x")
         sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.3)],
         ....:                xmin=0, xmax=2*pi, figsize=[2,1])
         sage: a                 # optional -- ImageMagick
@@ -200,13 +201,15 @@ class Animation(WithEqualityById, SageObject):
 
     We check that :trac:`7981` is fixed::
 
+        sage: x = SR.var("x")
         sage: a = animate([plot(sin(x + float(k)), (0, 2*pi), ymin=-5, ymax=5)
         ....:              for k in srange(0,2*pi,0.3)])
         sage: a.show() # optional -- ImageMagick
 
     Do not convert input iterator to a list, but ensure that
     the frame count is known after rendering the frames::
 
+        sage: x = SR.var("x")
         sage: a = animate((plot(x^p, (x,0,2)) for p in sxrange(1,2,.1)))
         sage: str(a)
         'Animation with unknown number of frames'
@@ -229,6 +232,7 @@ def __init__(self, v=None, **kwds):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.3)],
             ....:                xmin=0, xmax=2*pi, figsize=[2,1]) # indirect doctest
             sage: a           # optional -- ImageMagick
@@ -404,7 +408,7 @@ def make_image(self, frame, filename, **kwds):
             ....:        P = parametric_plot(frame[0], frame[1], **frame[2])
             ....:        P.save_image(filename,**kwds)
 
-            sage: t = var('t')
+            sage: t = SR.var("t")
             sage: x = lambda t: cos(t)
             sage: y = lambda n,t: sin(t)/n
             sage: B = MyAnimation([([x(t), y(i+1,t)],(t,0,1), {'color':Color((1,0,i/4)), 'aspect_ratio':1, 'ymax':1}) for i in range(4)])
@@ -451,6 +455,7 @@ def png(self, dir=None):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([plot(x^2 + n) for n in range(4)], ymin=0, ymax=4)
             sage: d = a.png(); v = os.listdir(d); v.sort(); v  # long time
             ['00000000.png', '00000001.png', '00000002.png', '00000003.png']
@@ -507,7 +512,7 @@ def graphics_array(self, ncols=3):
 
         Frames can be specified as a generator too; it is internally converted to a list::
 
-            sage: t = var('t')
+            sage: t = SR.var("t")
             sage: b = animate((plot(sin(c*pi*t)) for c in sxrange(1,2,.2)))
             sage: g = b.graphics_array()
             sage: g
@@ -557,6 +562,7 @@ def gif(self, delay=20, savefile=None, iterations=0, show_path=False,
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:             xmin=0, xmax=2*pi, ymin=-1, ymax=1, figsize=[2,1])
             sage: td = tmp_dir()
@@ -633,6 +639,7 @@ def _gif_from_imagemagick(self, savefile=None, show_path=False,
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:             xmin=0, xmax=2*pi, ymin=-1, ymax=1, figsize=[2,1])
             sage: td = tmp_dir()
@@ -692,6 +699,7 @@ def _rich_repr_(self, display_manager, **kwds):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([plot(x^2 + n) for n in range(4)], ymin=0, ymax=4)
             sage: from sage.repl.rich_output import get_display_manager
             sage: dm = get_display_manager()
@@ -784,6 +792,7 @@ def show(self, delay=None, iterations=None, **kwds):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:                xmin=0, xmax=2*pi, figsize=[2,1])
             sage: a.show()       # optional -- ImageMagick
@@ -896,6 +905,7 @@ def ffmpeg(self, savefile=None, show_path=False, output_format=None,
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:             xmin=0, xmax=2*pi, ymin=-1, ymax=1, figsize=[2,1])
             sage: td = tmp_dir()
@@ -1012,6 +1022,7 @@ def apng(self, savefile=None, show_path=False, delay=20, iterations=0):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:                xmin=0, xmax=2*pi, figsize=[2,1])
             sage: dir = tmp_dir()
@@ -1073,6 +1084,7 @@ def save(self, filename=None, show_path=False, use_ffmpeg=False, **kwds):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
             ....:             xmin=0, xmax=2*pi, ymin=-1, ymax=1, figsize=[2,1])
             sage: td = tmp_dir()
@@ -1151,6 +1163,7 @@ def interactive(self, **kwds):
 
         EXAMPLES::
 
+            sage: x = SR.var("x")
             sage: frames = [point3d((sin(x), cos(x), x)) for x in (0, pi/16, .., 2*pi)]
             sage: animate(frames).interactive(online=True)
             Graphics3d Object
@@ -1216,6 +1229,7 @@ class APngAssembler(object):
     EXAMPLES::
 
         sage: from sage.plot.animate import APngAssembler
+        sage: x = SR.var("x")
         sage: def assembleAPNG():
         ....:     a = animate([sin(x + float(k)) for k in srange(0,2*pi,0.7)],
         ....:                 xmin=0, xmax=2*pi, figsize=[2,1])