virtualenv is a tool that keep the depencies of the python project in a seperate place. To create a virtualenv you need to install this package first:

$sudo pip install virtualenv

Then you need to create a virtualenv, python2.7-venv is the name of the directory that save the copied python environment and the dependencies of the virtual environment:

$cd ~/
$virtualenv python2.7-venv

Then you need to activate the environment.

$source python2.7-venv/bin/activate

After that you can install packages to this virtual environment, these packages are isolated from the global environment.

$pip install pandas
$pip install matplotlib
$pip install pandas_datareader

To deactivate the environment:

$deactivate

Open "Project Structure", you can add a new SDK by selecting the python file under the bin directory of the virtual environment directory. The project will use this virtual environment to execute the python scripts.