title: Does a python virtual environment avoid redundant installs?
body: <p>I'm fairly new to python and I'm beginning to work with python virtual environments. When I create a virtual environment, I have to reinstall all the modules that I need for the current project that I'm working on. 
  I'm wondering if the virtual environment somehow avoids redundancies in installation of modules if the same version of the module had already been installed in another project or on a system-wide level?</p>
  
  <p>Also, would there be any point in installing modules on a system-wide level rather than just in virtual environments, since I would need to install the modules in the virtual environment anyway?</p>