| :orphan: | |
| .. include:: links.inc | |
| .. _virtual_envs: | |
| *************************** | |
| Python virtual environments | |
| *************************** | |
| If you plan to do regular work on astropy you should do your development in | |
| a python virtual environment. Conceptually a virtual environment is a | |
| duplicate of the python environment you normally work in with as many (or as | |
| few) of the packages from your normal environment included in that virtual | |
| environment. It is sandboxed from your normal python environment in the sense | |
| that packages installed in the virtual environment do not affect your normal | |
| environment in any way. | |
| .. note:: | |
| "Normal python environment" means whatever python you are using when you | |
| log in. | |
| There are two options for using virtual environments; the choice of method is | |
| dictated by the python distribution you use: | |
| * If you use the anaconda python distribution you must use `conda`_ to make | |
| and manage your virtual environments. | |
| * If you use any other distribution you use `virtualenvwrapper`_; you *can not* | |
| use `conda`_. As the name suggests, `virtualenvwrapper`_ is a wrapper around | |
| `virtualenv`_. | |
| In both cases you will go through the same basic steps; the commands to | |
| accomplish each step are given for both `conda`_ and `virtualenvwrapper`_: | |
| * :ref:`setup_for_env` | |
| * :ref:`list_env` | |
| * :ref:`create_env` | |
| * :ref:`activate_env` | |
| * :ref:`deactivate_env` | |
| * :ref:`delete_env` | |
| .. note:: | |
| + You **cannot** use `virtualenvwrapper`_ or `virtualenv`_ within anaconda. | |
| + `virtualenvwrapper`_ works with bash and bash-like shells; see | |
| :ref:`using-virtualenv` for alternatives. | |
| .. _setup_for_env: | |
| Set up for virtual environments | |
| =============================== | |
| * `virtualenvwrapper`_: | |
| + First, install `virtualenvwrapper`_, which will also install `virtualenv`_, | |
| with ``pip install virtualenvwrapper``. | |
| + From the `documentation for virtualenvwrapper`_, you also need to:: | |
| export WORKON_HOME=$HOME/.virtualenvs | |
| export PROJECT_HOME=$HOME/ | |
| source /usr/local/bin/virtualenvwrapper.sh | |
| * `conda`_: No setup is necessary beyond installing the anaconda python | |
| distribution. | |
| .. _list_env: | |
| List virtual environments | |
| ========================= | |
| You do not need to list the virtual environments you have created before using | |
| them...but sooner or later you will forget what environments you have defined | |
| and this is the easy way to find out. | |
| * `virtualenvwrapper`_: ``workon`` | |
| + If this displays nothing you have no virtual environments | |
| + If this displays ``workon: command not found`` then you haven't done | |
| the :ref:`setup_for_env`; do that. | |
| + For more detailed information about installed environments use | |
| ``lsvirtualenv``. | |
| * `conda`_: ``conda info -e`` | |
| + you will always have at least one environment, called ``root`` | |
| + your active environment is indicated by a ``*`` | |
| .. _create_env: | |
| Create a new virtual environment | |
| ================================ | |
| This needs to be done once for each virtual environment you want. There is one | |
| important choice you need to make when you create a virtual environment: | |
| which, if any, of the packages installed in your normal python environment do | |
| you want in your virtual environment? | |
| Including them in your virtual environment doesn't take much extra space--they | |
| are linked into the virtual environment instead of being copied. Within the | |
| virtual environment you can install new versions of packages like Numpy or | |
| Astropy that override the versions installed in your normal python environment. | |
| The easiest way to get started is to include in your virtual environment the | |
| packages installed in your your normal python environment; the instructions | |
| below do that. | |
| In everything that follows, ``ENV`` represents the name you give your virtual | |
| environment. | |
| **The name you choose cannot have spaces in it.** | |
| * `virtualenvwrapper`_: | |
| + Make an environment called ``ENV`` with all of the packages in your normal | |
| python environment:: | |
| mkvirtualenv --system-site-packages ENV | |
| + Omit the option ``--system-site-packages`` to create an environment | |
| without the python packages installed in your normal python environment. | |
| + Environments created with `virtualenvwrapper`_ always include `pip`_ | |
| and `setuptools <https://setuptools.readthedocs.io>`_ so that you | |
| can install packages within the virtual environment. | |
| + More details and examples are in the | |
| `virtualenvwrapper command documentation`_. | |
| * `conda`_: | |
| + Make an environment called ``ENV`` with all of the packages in your main | |
| anaconda environment:: | |
| conda create -n ENV anaconda | |
| + More details, and examples that start with none of the packages from | |
| your normal python environment, are in the | |
| `documentation for the conda command`_ and the | |
| `blog post announcing anaconda environments`_. | |
| + If astropy is installed in your environment, you may need to uninstall it | |
| in order for the development version to install properly. You can do this | |
| with the following command:: | |
| conda uninstall astropy | |
| .. _activate_env: | |
| Activate a virtual environment | |
| ============================== | |
| To use a new virtual environment you may need to activate it; | |
| `virtualenvwrapper`_ will try to automatically activate your new environment | |
| when you create it. Activation does two things (either of which you could do | |
| manually, though it would be inconvenient): | |
| * Put the ``bin`` directory for the virtual environment at the front of your | |
| ``$PATH``. | |
| * Add the name of the virtual environment to your command prompt. If you have | |
| successfully switched to a new environment called ``ENV`` your prompt should | |
| look something like this: ``(ENV)[~] $`` | |
| The commands below allow you to switch between virtual environments in | |
| addition to activating new ones. | |
| * `virtualenvwrapper`_: Activate the environment ``ENV`` with:: | |
| workon ENV | |
| * ` conda`: Activate the environment ``ENV`` with:: | |
| source activate ENV | |
| .. _deactivate_env: | |
| Deactivate a virtual environment | |
| ================================ | |
| At some point you may want to go back to your normal python environment. Do | |
| that with: | |
| * `virtualenvwrapper`_: ``deactivate`` | |
| + Note that in ``virtualenvwrapper 4.1.1`` the output of | |
| ``mkvirtualenv`` says you should use ``source deactivate``; that does | |
| not seem to actually work. | |
| * `conda`_: ``source deactivate`` | |
| .. _delete_env: | |
| Delete a virtual environment | |
| ============================ | |
| In both `virtualenvwrapper`_ and `conda`_ you can simply delete the directory in | |
| which the ``ENV`` is located; both also provide commands to make that a bit easier. | |
| * `virtualenvwrapper`_: ``rmvirtualenv ENV`` | |
| * `conda`_: ``conda remove --all -n ENV`` | |
| .. _documentation for virtualenvwrapper: http://virtualenvwrapper.readthedocs.io/en/latest/install.html | |
| .. _virtualenvwrapper command documentation: http://virtualenvwrapper.readthedocs.io/en/latest/command_ref.html | |
| .. _documentation for the conda command: https://docs.conda.io/projects/conda/en/latest/commands.html | |
| .. _blog post announcing anaconda environments: https://www.anaconda.com/category/developer-blog/ | |