title: Python: i cant do substitution
body: <p>I'm using python2.7</p>
  <p>I ran this code</p>
  <pre><code>print r.data
  print r[0][action-1].data
  </code></pre>
  <p>then it throws this.</p>
  <blockquote>
  <p>[[ 0.34642464  0.39359313 -1.24270797 -0.89923799  0.11451679 -0.49929592]]</p>
  <p>-0.499295920134</p>
  </blockquote>
  <p>then, i tried to substitution &quot;r&quot; like this</p>
  <pre><code>r[0][action-1].data = 1
  </code></pre>
  <p>but i couldn't.</p>
  <pre><code>print r[0][action-1].data
  </code></pre>
  <blockquote>
  <p>-0.499295920134</p>
  </blockquote>
  <p>what's my problem?
  i imported this.</p>
  <pre><code>import numpy as np　　　　　　　　
  import matplotlib.pyplot as plt
  import cv2
  import random
  import chainer
  from chainer import cuda
  from chainer import serializers
  import chainer.functions as F
  from chainer import optimizers
  </code></pre>
  <p><code>print(type(r))</code> is</p>
  <blockquote>
  <p>class 'chainer.variable.Variable'</p>
  </blockquote>
  <pre><code>print (type(r[0])
  </code></pre>
  <p>is also</p>
  <blockquote>
  <p>class 'chainer.variable.Variable'</p>
  </blockquote>
  <p>　　</p>