title: How to use pyunpack to unpack .7z file?
body: <p>Im trying to unpack a 7z file but got an error.</p>
  
  <p>This is the code:</p>
  
  <pre><code>from pyunpack import Archive
  Archive('E:/Desktop/vnpt2/2_1_0_2841.7z').extractall('E:/Desktop/vnpt2/new')
  </code></pre>
  
  <p>And this is error:</p>
  
  <pre class="lang-none prettyprint-override"><code>Traceback (most recent call last):
    File "E:\Desktop\vnpt2\zip.py", line 2, in &lt;module&gt;
      Archive('E:/Desktop/vnpt2/2_1_0_2841.7z').extractall('E:/Desktop/vnpt2/new')
    File "C:\Python27\lib\site-packages\pyunpack\__init__.py", line 90, in extractall
      self.extractall_patool(directory, patool_path)
    File "C:\Python27\lib\site-packages\pyunpack\__init__.py", line 62, in extractall_patool
      raise PatoolError('patool can not unpack\n' + str(p.stderr))
  pyunpack.PatoolError: patool can not unpack
  patool error: error extracting E:\Desktop\vnpt2\2_1_0_2841.7z: could not find an executable program to extract format 7z; candidates are (7z,7za,7zr),
  </code></pre>
  
  <p>How can I fix it?</p>