.. _virtualenvironments-ref:

Pipenv & Virtual Environments

.. image:: /_static/photos/35294660055_42c02b2316_k_d.jpg

This tutorial walks you through installing and using Python packages.

It will show you how to install and use the necessary tools and make strong

recommendations on best practices. Keep in mind that Python is used for a great

many different purposes, and precisely how you want to manage your dependencies

may change based on how you decide to publish your software. The guidance

presented here is most directly applicable to the development and deployment of

network services (including web applications), but is also very well suited to

managing development and testing environments for any kind of project.

.. Note:: This guide is written for Python 3, however, these instructions

should work fine on Python 2.7—if you are still using it, for some reason.

Make sure you've got Python & pip

Before you go any further, make sure you have Python and that it's available

from your command line. You can check this by simply running:

.. code-block:: bash

You should get some output like ``3.6.2``. If you do not have Python, please

install the latest 3.x version from `python.org`_ or refer to the

`Installing Python`_ section of this guide.

.. Note:: If you're newcomer and you get an error like this:

.. code-block:: python

It's because this command is intended to be run in a *shell* (also called

a *terminal* or *console*). See the Python for Beginners

`getting started tutorial`_ for an introduction to using your operating

system's shell and interacting with Python.

Additionally, you'll need to make sure you have `pip`_ available. You can

check this by running:

.. code-block:: bash

If you installed Python from source, with an installer from `python.org`_, or

via `Homebrew`_ you should already have pip. If you're on Linux and installed

using your OS package manager, you may have to `install pip <https://pip.pypa.io/en/stable/installing/>`_ separately.

.. _getting started tutorial: https://opentechschool.github.io/python-beginners/en/getting_started.html#what-is-python-exactly

.. _python.org: https://python.org

.. _pip: https://pypi.org/project/pip/

.. _Homebrew: https://brew.sh

.. _Installing Python: https://docs.python-guide.org/starting/installation/

Installing Pipenv

`Pipenv`_ is a dependency manager for Python projects. If you're familiar

with Node.js' `npm`_ or Ruby's `bundler`_, it is similar in spirit to those

tools. While `pip`_ can install Python packages, Pipenv is recommended as

it's a higher-level tool that simplifies dependency management for common use

cases.

Use ``pip`` to install Pipenv:

.. code-block:: console

.. Note:: This does a `user installation`_ to prevent breaking any system-wide

packages. If ``pipenv`` isn't available in your shell after installation,

you'll need to add the `user base`_'s binary directory to your ``PATH``.

On Linux and macOS you can find the user base binary directory by running

``python -m site --user-base`` and adding ``bin`` to the end. For example,

this will typically print ``~/.local`` (with ``~`` expanded to the

absolute path to your home directory) so you'll need to add

``~/.local/bin`` to your ``PATH``. You can set your ``PATH`` permanently by

`modifying ~/.profile`_.

On Windows you can find the user base binary directory by running

``py -m site --user-site`` and replacing ``site-packages`` with

``Scripts``. For example, this could return

``C:\Users\Username\AppData\Roaming\Python36\site-packages`` so you would

need to set your ``PATH`` to include

``C:\Users\Username\AppData\Roaming\Python36\Scripts``. You can set your

user ``PATH`` permanently in the `Control Panel`_. You may need to log

out for the ``PATH`` changes to take effect.

.. _Pipenv: https://docs.pipenv.org/

.. _npm: https://www.npmjs.com/

.. _bundler: http://bundler.io/

.. _user base: https://docs.python.org/3/library/site.html#site.USER_BASE

.. _user installation: https://pip.pypa.io/en/stable/user_guide/#user-installs

.. _modifying ~/.profile: https://stackoverflow.com/a/14638025

.. _Control Panel: https://msdn.microsoft.com/en-us/library/windows/desktop/bb776899(v=vs.85).aspx

Installing packages for your project

Pipenv manages dependencies on a per-project basis. To install packages,

change into your project's directory (or just an empty directory for this

tutorial) and run:

.. code-block:: bash

Pipenv will install the excellent `Requests`_ library and create a ``Pipfile``

for you in your project's directory. The `Pipfile`_ is used to track which

dependencies your project needs in case you need to re-install them, such as

when you share your project with others. You should get output similar to this

(although the exact paths shown will vary):

.. _Pipfile: https://github.com/pypa/pipfile

.. code-block:: text

.. _Requests: https://python-requests.org

Using installed packages

Now that Requests is installed you can create a simple ``main.py`` file to

use it:

.. code-block:: python

Then you can run this script using ``pipenv run``:

.. code-block:: bash

You should get output similar to this:

.. code-block:: text

Using ``$ pipenv run`` ensures that your installed packages are available to

your script. It's also possible to spawn a new shell that ensures all commands

have access to your installed packages with ``$ pipenv shell``.

Next steps

Congratulations, you now know how to install and use Python packages! ✨ 🍰 ✨

Lower level: virtualenv

`virtualenv <http://pypi.python.org/pypi/virtualenv>`_ is a tool to create

isolated Python environments. virtualenv creates a folder which contains all the

necessary executables to use the packages that a Python project would need.

It can be used standalone, in place of Pipenv.

Install virtualenv via pip:

.. code-block:: console

Test your installation

.. code-block:: console

Basic Usage

1. Create a virtual environment for a project:

.. code-block:: console

``virtualenv my_project`` will create a folder in the current directory which will

contain the Python executable files, and a copy of the ``pip`` library which you

can use to install other packages. The name of the virtual environment (in this

case, it was ``my_project``) can be anything; omitting the name will place the files

in the current directory instead.

This creates a copy of Python in whichever directory you ran the command in,

placing it in a folder named :file:`my_project`.

You can also use the Python interpreter of your choice (like

``python2.7``).

.. code-block:: console

or change the interpreter globally with an env variable in ``~/.bashrc``:

.. code-block:: console

2. To begin using the virtual environment, it needs to be activated:

.. code-block:: console

The name of the current virtual environment will now appear on the left of

the prompt (e.g. ``(my_project)Your-Computer:your_project UserName$)`` to let you know

that it's active. From now on, any package that you install using pip will be

placed in the ``my_project`` folder, isolated from the global Python installation.

Install packages as usual, for example:

.. code-block:: console

3. If you are done working in the virtual environment for the moment, you can

deactivate it:

.. code-block:: console

This puts you back to the system's default Python interpreter with all its

installed libraries.

To delete a virtual environment, just delete its folder. (In this case,

it would be ``rm -rf my_project``.)

After a while, though, you might end up with a lot of virtual environments

littered across your system, and its possible you'll forget their names or

where they were placed.

Other Notes

Running ``virtualenv`` with the option ``--no-site-packages`` will not

include the packages that are installed globally. This can be useful

for keeping the package list clean in case it needs to be accessed later.

[This is the default behavior for ``virtualenv`` 1.7 and later.]

In order to keep your environment consistent, it's a good idea to "freeze"

the current state of the environment packages. To do this, run

.. code-block:: console

This will create a :file:`requirements.txt` file, which contains a simple

list of all the packages in the current environment, and their respective

versions. You can see the list of installed packages without the requirements

format using "pip list". Later it will be easier for a different developer

(or you, if you need to re-create the environment) to install the same packages

using the same versions:

.. code-block:: console

This can help ensure consistency across installations, across deployments,

and across developers.

Lastly, remember to exclude the virtual environment folder from source

control by adding it to the ignore list (see :ref:`Version Control Ignores<version_control_ignores>`).

.. _virtualenvwrapper-ref:

virtualenvwrapper

`virtualenvwrapper <https://virtualenvwrapper.readthedocs.io/en/latest/index.html>`_

provides a set of commands which makes working with virtual environments much

more pleasant. It also places all your virtual environments in one place.

To install (make sure **virtualenv** is already installed):

.. code-block:: console

(`Full virtualenvwrapper install instructions <https://virtualenvwrapper.readthedocs.io/en/latest/install.html>`_.)

For Windows, you can use the `virtualenvwrapper-win <https://github.com/davidmarble/virtualenvwrapper-win/>`_.

To install (make sure **virtualenv** is already installed):

.. code-block:: console

In Windows, the default path for WORKON_HOME is %USERPROFILE%\Envs

Basic Usage

1. Create a virtual environment:

.. code-block:: console

This creates the :file:`my_project` folder inside :file:`~/Envs`.

2. Work on a virtual environment:

.. code-block:: console

Alternatively, you can make a project, which creates the virtual environment,

and also a project directory inside ``$WORKON_HOME``, which is ``cd`` -ed into

when you ``workon myproject``.

.. code-block:: console

**virtualenvwrapper** provides tab-completion on environment names. It really

helps when you have a lot of environments and have trouble remembering their

names.

``workon`` also deactivates whatever environment you are currently in, so you

can quickly switch between environments.

3. Deactivating is still the same:

.. code-block:: console

4. To delete:

.. code-block:: console

Other useful commands

``lsvirtualenv``

List all of the environments.

``cdvirtualenv``

Navigate into the directory of the currently activated virtual environment,

so you can browse its :file:`site-packages`, for example.

``cdsitepackages``

Like the above, but directly into :file:`site-packages` directory.

``lssitepackages``

Shows contents of :file:`site-packages` directory.

`Full list of virtualenvwrapper commands <https://virtualenvwrapper.readthedocs.io/en/latest/command_ref.html>`_.

virtualenv-burrito

With `virtualenv-burrito <https://github.com/brainsik/virtualenv-burrito>`_, you

can have a working virtualenv + virtualenvwrapper environment in a single command.

autoenv

When you ``cd`` into a directory containing a :file:`.env`, `autoenv <https://github.com/kennethreitz/autoenv>`_

automagically activates the environment.

Install it on Mac OS X using ``brew``:

.. code-block:: console

And on Linux:

.. code-block:: console