| :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/ |
|
|
|
|
