title: NameError: name 'nltk' is not defined
body: <p>I have a Python notebook that used to work before without problems.
  Now if I try to run it, I get an &quot;NameError: name 'nltk' is not defined&quot; error.
  I'm not sure what has changed since on my system.
  I tried so far:</p>
  <ol>
  <li>Installing nltk library with pip</li>
  <li>Downloading nltk library with python interpreter</li>
  </ol>
  <pre class="lang-sh prettyprint-override"><code>pip3 install nltk 
  
  Requirement already satisfied: nltk in /Applications/anaconda3/lib/python3.8/site-packages (3.5)
  
  python
  &gt;&gt;&gt;import nltk
  &gt;&gt;&gt;nltk.download('all')
  </code></pre>
  <pre class="lang-sh prettyprint-override"><code>$ which python python2 python3
  
  /Applications/anaconda3/bin/python
  /usr/bin/python2
  /Applications/anaconda3/bin/python3
  
  $ which pip pip2 pip3
  
  /Applications/anaconda3/bin/pip
  /Applications/anaconda3/bin/pip3
  
  $ python3 --version
  Python 3.8.3
  
  $ echo $PATH
  /Applications/anaconda3/bin:/Applications/anaconda3/condabin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/testimo/.rvm/bin:/Users/testimo/.rvm/bin
  </code></pre>
  <p>Is this path wrong? How can I fix it?
  Or any other tips? Thank you!</p>