Python Virtualenv on OSX

Install virtualenv

Johns-MBP:~ johnroberts$ pip install virtualenv

Johns-MBP:~ johnroberts$ mkdir -p ~/Virtualenvs

Johns-MBP:~ johnroberts$ mkdir -p ~/Projects

Johns-MBP:~ johnroberts$ cd ~/Virtualenvs/

Create the virtual environments

Johns-MBP:~ johnroberts$ virtualenv foobar

New python executable in foobar/bin/python2.7

Also creating executable in foobar/bin/python

Installing setuptools, pip, wheel...done.

Johns-MBP:~ johnroberts$ virtualenv -p python3 foobar-py3

Running virtualenv with interpreter /usr/local/bin/python3

Using base prefix '/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5'

New python executable in foobar-py3/bin/python3.5

Also creating executable in foobar-py3/bin/python

Installing setuptools, pip, wheel...done.

This should get Virtualenv in place.

Activate an environment

We made the Python environment, now we need to activate it.

Johns-MBP:~ johnroberts$ source foobar/bin/activate

(foobar)Johns-MBP:~ johnroberts$ 

Notice the "(foobar)" which shows that we are now in the environment.

What version of python are we using

We can check which version of python

(foobar)Johns-MBP:~ johnroberts$ which python

/Users/johnroberts/foobar/bin/python

This shows that we are using python from our environment.

(foobar)Johns-MBP:~ johnroberts$ python --version

Python 2.7.10

We can also check pip

(foobar)Johns-MBP:~ johnroberts$ which pip

/Users/johnroberts/foobar/bin/pip

Use pip to see what packages are here

(foobar)Johns-MBP:~ johnroberts$ pip list

pip (7.1.2)

setuptools (18.2)

wheel (0.24.0)

If I did pip list outside of this environment I'd get a lot of packages (I won't list them here)

Install the packages for this environment

(foobar)Johns-MBP:~ johnroberts$ pip install numpy

Collecting numpy

  Downloading numpy-1.10.2-cp27-none-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl (3.7MB)

    100% |████████████████████████████████| 3.7MB 143kB/s 

Installing collected packages: numpy

Successfully installed numpy-1.10.2

Cool as a cucumber.

List of Dependencies

Make a list of dependencies for this project and view it using cat

(foobar)Johns-MBP:~ johnroberts$ pip freeze --local > requirements.txt

(foobar)Johns-MBP:~ johnroberts$ cat requirements.txt 

numpy==1.10.2

wheel==0.24.0

The list of dependencies is very useful for recreating other environments using pip. Create the environment and then use pip and the requirements.txt file to install the dependencies.

    pip install -r requirements.txt

Get out of the environment - deactivate

We just type deactivate

(foobar)Johns-MBP:~ johnroberts$ deactivate

Johns-MBP:~ johnroberts$ 

Notice that "(foobar)" has been removed. We are no longer in that environment.

Remove the Virtual Environment
Once deactivated, we can remove:

Johns-MBP:~ johnroberts$ rm -rf foobar/

Simple.