<div class="section" id="variable-inheritance">
<span id="index-0"></span><span id="id1"></span>
<div class="line-block">
<div class="line">In the previous chapter, we saw how to define a <a class="reference internal" href="../../../glossary/#term-variable"><em class="xref std std-term">variable</em></a> for a <a class="reference internal" href="../../../glossary/#term-task"><em class="xref std std-term">task</em></a>.</div>
<div class="line">When all the tasks of the same <a class="reference internal" href="../../../glossary/#term-family"><em class="xref std std-term">family</em></a> share the same variable value,</div>
<div class="line">the value could be defined at the family level.</div>
<div class="line">This is termed <a class="reference internal" href="../../../glossary/#term-variable-inheritance"><em class="xref std std-term">variable inheritance</em></a></div>
</div>
<div class="highlight-python"><pre># Definition of the suite test.
suite test
   edit ECF_INCLUDE "$HOME/course"
   edit ECF_HOME    "$HOME/course"
   family f1
      edit SLEEP 20
      task t1
      task t2
   endfamily
endsuite</pre>
</div>
<p>Or in python:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="c">#!/usr/bin/env python2.5</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">ecflow</span>  

<span class="k">def</span> <span class="nf">create_family_f1</span><span class="p">():</span>
    <span class="n">f1</span> <span class="o">=</span> <span class="n">ecflow</span><span class="o">.</span><span class="n">Family</span><span class="p">(</span><span class="s">&quot;f1&quot;</span><span class="p">)</span>
    <span class="n">f1</span><span class="o">.</span><span class="n">add_variable</span><span class="p">(</span><span class="s">&quot;SLEEP&quot;</span><span class="p">,</span><span class="mi">20</span><span class="p">)</span>
    <span class="n">f1</span><span class="o">.</span><span class="n">add_task</span><span class="p">(</span><span class="s">&quot;t1&quot;</span><span class="p">)</span>
    <span class="n">f1</span><span class="o">.</span><span class="n">add_task</span><span class="p">(</span><span class="s">&quot;t2&quot;</span><span class="p">)</span>
    <span class="k">return</span> <span class="n">f1</span>         
      
<span class="n">defs</span> <span class="o">=</span> <span class="n">ecflow</span><span class="o">.</span><span class="n">Defs</span><span class="p">(</span><span class="s">&quot;test.def&quot;</span><span class="p">)</span>
<span class="n">suite</span> <span class="o">=</span> <span class="n">defs</span><span class="o">.</span><span class="n">add_suite</span><span class="p">(</span><span class="s">&quot;test&quot;</span><span class="p">)</span>
<span class="n">suite</span><span class="o">.</span><span class="n">add_variable</span><span class="p">(</span><span class="s">&quot;ECF_INCLUDE&quot;</span><span class="p">,</span><span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s">&quot;HOME&quot;</span><span class="p">)</span> <span class="o">+</span> <span class="s">&quot;/course&quot;</span><span class="p">)</span>
<span class="n">suite</span><span class="o">.</span><span class="n">add_variable</span><span class="p">(</span><span class="s">&quot;ECF_HOME   &quot;</span><span class="p">,</span><span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s">&quot;HOME&quot;</span><span class="p">)</span> <span class="o">+</span> <span class="s">&quot;/course&quot;</span><span class="p">)</span>

<span class="n">suite</span><span class="o">.</span><span class="n">add_family</span><span class="p">(</span> <span class="n">create_family_f1</span><span class="p">()</span> <span class="p">)</span>
</pre></div>
</div>
<div class="line-block">
<div class="line">The <a class="reference internal" href="../../../glossary/#term-variable"><em class="xref std std-term">variable</em></a> could have been defined at the level of the <a class="reference internal" href="../../../glossary/#term-suite"><em class="xref std std-term">suite</em></a>,</div>
<div class="line">achieving the same results. Variables are inherited from the parent node.</div>
<div class="line">If a variable is redefined lower in the tree, it is said to be overridden.</div>
<div class="line">In this case the new definition is the one being used.</div>
<div class="line">It is possible to override generated variables.</div>
<div class="line">This is not recommended and you should understand all the consequences</div>
<div class="line">if you decide to do so.</div>
</div>
<p>Let us have a quiz. Consider the following suite:</p>
<div class="highlight-python"><pre>suite test
   edit SLEEP 100
   family f1
      edit SLEEP 80
      task t1
      task t2
         edit SLEEP 9
      family g1
          edit SLEEP 89
          task x1
              edit SLEEP 10
          task x2
      endfamily
   endfamily
   family f2
     task t1
     task t2
         edit SLEEP 77
     family g2
          task x1
              edit SLEEP 12
          task x2
      endfamily
   endfamily
endsuite</pre>
</div>
<p>What is the value of the <a class="reference internal" href="../../../glossary/#term-variable"><em class="xref std std-term">variable</em></a> SLEEP for:</p>
<blockquote>
<div><table border="1" class="docutils">
<colgroup>
<col width="70%" />
<col width="30%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head"><a class="reference internal" href="../../../glossary/#term-node"><em class="xref std std-term">node</em></a></th>
<th class="head">SLEEP</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>test/f1/t1</td>
<td>?</td>
</tr>
<tr><td>/test/f1/t2</td>
<td>?</td>
</tr>
<tr><td>/test/f1/g1/x1</td>
<td>?</td>
</tr>
<tr><td>/test/f1/g1/x2</td>
<td>?</td>
</tr>
<tr><td>/test/f2/t1</td>
<td>?</td>
</tr>
<tr><td>/test/f2/t2</td>
<td>?</td>
</tr>
<tr><td>/test/f2/g2/x1</td>
<td>?</td>
</tr>
<tr><td>/test/f2/g2/x2</td>
<td>?</td>
</tr>
</tbody>
</table>
</div></blockquote>
</div>