unable to install package using pip
<p>I am trying to install module using pip and I get this error:</p>

<pre class="lang-none prettyprint-override"><code>$ pip install virtualenv

Collecting virtualenv
  Downloading virtualenv-15.0.3-py2.py3-none-any.whl (3.5MB)
    100% |ââââââââââââââââââââââââââââââââ| 3.5MB 312kB/s
Installing collected packages: virtualenv
Exception:
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/commands/install.py", line 317, in run
    prefix=options.prefix_path,
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/req/req_set.py", line 742, in install
    **kwargs
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/req/req_install.py", line 831, in install
    self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/req/req_install.py", line 1032, in move_wheel_files
    isolated=self.isolated,
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/wheel.py", line 346, in move_wheel_files
    clobber(source, lib_dir, True)
  File "/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg/pip/wheel.py", line 324, in clobber
    shutil.copyfile(srcfile, destfile)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 83, in copyfile
    with open(dst, 'wb') as fdst:
IOError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/virtualenv.py'
</code></pre>

<p>What is the problem and how can I resolve it?</p>

<p>the problem is caused because you have not given the super user permission to the system. in order to make any changes into the system you should go to super user mode, for that you have to type the code as</p>

<pre><code>sudo pip install virtualenv
</code></pre>

<p>it will help you out </p>

python pip