title: How to use python call a C++ dll which depends on other dll
body: <p>Description:
  I got two C++ classes named <em>bclass</em> and <em>nclass</em>. Both of two classes have made by .so already. My target is to use python to create a <em>nclass</em> and call a method named add in <em>nclass</em>. By the way, <em>nclass</em> depends on <em>bclass</em>. I plan to use ctypes module, but when a write the code <code>&quot;lib=CDLL(&quot;./libnclass.so&quot;)&quot;</code></p>
  <p>an error comes and show that</p>
  <blockquote>
  <p>&quot;OSError: libbclass.so: cannot open shared object file:No such file or
  directory&quot;</p>
  </blockquote>
  <p>When I just call libbclass.so program is OK</p>
  <p>So I got two questions,</p>
  <p><strong>first,</strong></p>
  <p>how do I call <em>nclass</em> in python,</p>
  <p><strong>second</strong></p>
  <p>how do I create an object by <em>nclass</em> and using some method in <em>nclass</em></p>