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Switching between Python 2 and Python 3 environments
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You can easily maintain separate environments for Python 2 programs and
Python 3 programs on the same computer, without worrying about the programs
interacting with each other. Switching to an environment is called activating it.

Summary
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#. Create a Python 2 environment
#. Create a Python 3 environment
#. Activate and use the Python 2 environment
#. Deactivate the Python 2 environment
#. Activate and use the Python 3 environment
#. Deactivate the Python 3 environment

Create a Python 2 environment named py2, install Python 2.7::

  conda create --name py2 python=2.7

Create a new environment named py3, install Python 3.5::

  conda create --name py3 python=3.5

Now you have two environments to work with. You can install packages and
run programs as desired in either one.

Activate and use the Python 2 environment

WINDOWS::

 activate py2

LINUX, macOS::

  source activate py2

Use your py2 environment to install packages and run programs as desired.
When finished, deactivate the environment

WINDOWS::

 deactivate

macOS, LINUX::

  source deactivate

Activate and use the Python 3 environment

WINDOWS::

 activate py3

LINUX, macOS::

  source activate py3

Use the py3 environment to install and run programs as desired. When
finished, deactivate the environment

WINDOWS::

 deactivate

macOS, LINUX::

  source deactivate
