title: How to import physical constants from scipy.constants.physical_constants?
body: <p>I'm trying to import the <code>electron volt-joule relationship</code> from <code>scipy.constants.physical_constants</code> for use in a numerical physics problem. This is probably a very simple issue, or a misunderstanding of the physical_constants dictionary, but after googling for 2 hrs I'm still at a loss.</p>
  <p>I've tried</p>
  <p><code>from scipy.constants.physical_constants import electron volt_joule relationship</code></p>
  <p>I also tried</p>
  <p><code>import scipy.constants.physical_constants[&quot;electron volt-joule relationship&quot;]</code></p>
  <p>Which produces</p>
  <p><code>File &quot;&lt;ipython-input-22-7c2fb3ec2156&gt;&quot;, line 3 import scipy.constants.physical_constants[&quot;electron volt-joule relationship&quot;] ^ SyntaxError: invalid syntax</code></p>
  <p>Am I misunderstanding the use of these physical constants? From scipy.org documentation I'm seeing that they come in the form physical_constants[name] = (value, unit, uncertainty)</p>
  <p>so I can get</p>
  <p><code>print(scipy.constants.physical_constants[&quot;electron volt-joule relationship&quot;])</code></p>
  <p>to return</p>
  <p><code>(1.602176634e-19, 'J', 0.0)</code></p>
  <p>but even</p>
  <p><code>import scipy.constants.physical_constants</code></p>
  <p>returns an error of</p>
  <pre><code>ModuleNotFoundError                       Traceback (most recent call last)
  &lt;ipython-input-21-b4d34ca28080&gt; in &lt;module&gt; 
  ----&gt; 1 import scipy.constants.physical_constants
  
  ModuleNotFoundError: No module named 'scipy.constants.physical_constants'
  </code></pre>
  <p>Is this constants library full of values you can reference the value, unit, and uncertainty of and not actually use in computations?</p>