Pipenv & Virtual Environments¶
This tutorial walks you through installing and using Python packages.
It will show you how to install and use the necessary tools and make strongrecommendations on best practices. Keep in mind that Python is used for a greatmany different purposes, and precisely how you want to manage your dependenciesmay change based on how you decide to publish your software. The guidancepresented here is most directly applicable to the development and deployment ofnetwork services (including web applications), but is also very well suited tomanaging development and testing environments for any kind of project.
Note
This guide is written for Python 3, however, these instructionsshould 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 availablefrom your command line. You can check this by simply running:
$ python --version
You should get some output like3.6.2. If you do not have Python, pleaseinstall the latest 3.x version frompython.org or refer to theInstalling Python section of this guide.
Note
If you’re newcomer and you get an error like this:
>>>pythonTraceback (most recent call last): File"<stdin>", line1, in<module>NameError:name 'python' is not defined
It’s because this command is intended to be run in ashell (also calledaterminal orconsole). See the Python for Beginnersgetting started tutorial for an introduction to using your operatingsystem’s shell and interacting with Python.
Additionally, you’ll need to make sure you havepip available. You cancheck this by running:
$ pip --version
If you installed Python from source, with an installer frompython.org, orviaHomebrew you should already have pip. If you’re on Linux and installedusing your OS package manager, you may have toinstall pip separately.
Installing Pipenv¶
Pipenv is a dependency manager for Python projects. If you’re familiarwith Node.js’npm or Ruby’sbundler, it is similar in spirit to thosetools. Whilepip can install Python packages, Pipenv is recommended asit’s a higher-level tool that simplifies dependency management for common usecases.
Usepip to install Pipenv:
$ pip install --user pipenv
Note
This does auser installation to prevent breaking any system-widepackages. Ifpipenv isn’t available in your shell after installation,you’ll need to add theuser base‘s binary directory to yourPATH.
On Linux and macOS you can find the user base binary directory by runningpython-msite--user-base and addingbin to the end. For example,this will typically print~/.local (with~ expanded to theabsolute path to your home directory) so you’ll need to add~/.local/bin to yourPATH. You can set yourPATH permanently bymodifying ~/.profile.
On Windows you can find the user base binary directory by runningpy-msite--user-site and replacingsite-packages withScripts. For example, this could returnC:\Users\Username\AppData\Roaming\Python36\site-packages so you wouldneed to set yourPATH to includeC:\Users\Username\AppData\Roaming\Python36\Scripts. You can set youruserPATH permanently in theControl Panel. You may need to logout for thePATH changes to take effect.
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 thistutorial) and run:
$cd myproject$ pipenv install requestsPipenv will install the excellentRequests library and create aPipfilefor you in your project’s directory. ThePipfile is used to track whichdependencies your project needs in case you need to re-install them, such aswhen you share your project with others. You should get output similar to this(although the exact paths shown will vary):
Creating a Pipfile for this project...Creating a virtualenv for this project...Using base prefix '/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6'New python executable in ~/.local/share/virtualenvs/tmp-agwWamBd/bin/python3.6Also creating executable in ~/.local/share/virtualenvs/tmp-agwWamBd/bin/pythonInstalling setuptools, pip, wheel...done.Virtualenv location: ~/.local/share/virtualenvs/tmp-agwWamBdInstalling requests...Collecting requests Using cached requests-2.18.4-py2.py3-none-any.whlCollecting idna<2.7,>=2.5 (from requests) Using cached idna-2.6-py2.py3-none-any.whlCollecting urllib3<1.23,>=1.21.1 (from requests) Using cached urllib3-1.22-py2.py3-none-any.whlCollecting chardet<3.1.0,>=3.0.2 (from requests) Using cached chardet-3.0.4-py2.py3-none-any.whlCollecting certifi>=2017.4.17 (from requests) Using cached certifi-2017.7.27.1-py2.py3-none-any.whlInstalling collected packages: idna, urllib3, chardet, certifi, requestsSuccessfully installed certifi-2017.7.27.1 chardet-3.0.4 idna-2.6 requests-2.18.4 urllib3-1.22Adding requests to Pipfile's [packages]...P.S. You have excellent taste! ✨ 🍰 ✨
Using installed packages¶
Now that Requests is installed you can create a simplemain.py file touse it:
importrequestsresponse=requests.get('https://httpbin.org/ip')print('Your IP is {0}'.format(response.json()['origin']))
Then you can run this script usingpipenvrun:
$ pipenv run python main.py
You should get output similar to this:
Your IP is 8.8.8.8
Using$pipenvrun ensures that your installed packages are available toyour script. It’s also possible to spawn a new shell that ensures all commandshave access to your installed packages with$pipenvshell.
Next steps¶
Congratulations, you now know how to install and use Python packages! ✨ 🍰 ✨
Lower level: virtualenv¶
virtualenv is a tool to createisolated Python environments. virtualenv creates a folder which contains all thenecessary executables to use the packages that a Python project would need.
It can be used standalone, in place of Pipenv.
Install virtualenv via pip:
$ pip install virtualenvTest your installation
$ virtualenv --version- Create a virtual environment for a project:
$cd my_project_folder$ virtualenv my_project
virtualenvmy_project will create a folder in the current directory which willcontain the Python executable files, and a copy of thepip library which youcan use to install other packages. The name of the virtual environment (in thiscase, it wasmy_project) can be anything; omitting the name will place the filesin the current directory instead.
This creates a copy of Python in whichever directory you ran the command in,placing it in a folder namedmy_project.
You can also use the Python interpreter of your choice (likepython2.7).
$ virtualenv -p /usr/bin/python2.7 my_projector change the interpreter globally with an env variable in~/.bashrc:
$exportVIRTUALENVWRAPPER_PYTHON=/usr/bin/python2.7
- To begin using the virtual environment, it needs to be activated:
$source my_project/bin/activate
The name of the current virtual environment will now appear on the left ofthe prompt (e.g.(my_project)Your-Computer:your_projectUserName$) to let you knowthat it’s active. From now on, any package that you install using pip will beplaced in themy_project folder, isolated from the global Python installation.
Install packages as usual, for example:
$ pip install requests- If you are done working in the virtual environment for the moment, you candeactivate it:
$ deactivateThis puts you back to the system’s default Python interpreter with all itsinstalled libraries.
To delete a virtual environment, just delete its folder. (In this case,it would berm-rfmy_project.)
After a while, though, you might end up with a lot of virtual environmentslittered across your system, and its possible you’ll forget their names orwhere they were placed.
Runningvirtualenv with the option--no-site-packages will notinclude the packages that are installed globally. This can be usefulfor keeping the package list clean in case it needs to be accessed later.[This is the default behavior forvirtualenv 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
$ pip freeze > requirements.txtThis will create arequirements.txt file, which contains a simplelist of all the packages in the current environment, and their respectiveversions. You can see the list of installed packages without the requirementsformat 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 packagesusing the same versions:
$ pip install -r requirements.txtThis can help ensure consistency across installations, across deployments,and across developers.
Lastly, remember to exclude the virtual environment folder from sourcecontrol by adding it to the ignore list (seeVersion Control Ignores).
virtualenvwrapper¶
virtualenvwrapperprovides a set of commands which makes working with virtual environments muchmore pleasant. It also places all your virtual environments in one place.
To install (make surevirtualenv is already installed):
$ pip install virtualenvwrapper$exportWORKON_HOME=~/Envs$source /usr/local/bin/virtualenvwrapper.sh
(Full virtualenvwrapper install instructions.)
For Windows, you can use thevirtualenvwrapper-win.
To install (make surevirtualenv is already installed):
$ pip install virtualenvwrapper-winIn Windows, the default path for WORKON_HOME is %USERPROFILE%Envs
Basic Usage¶
- Create a virtual environment:
$ mkvirtualenv my_projectThis creates themy_project folder inside~/Envs.
- Work on a virtual environment:
$ workon my_projectAlternatively, you can make a project, which creates the virtual environment,and also a project directory inside$WORKON_HOME, which iscd -ed intowhen youworkonmyproject.
$ mkproject myprojectvirtualenvwrapper provides tab-completion on environment names. It reallyhelps when you have a lot of environments and have trouble remembering theirnames.
workon also deactivates whatever environment you are currently in, so youcan quickly switch between environments.
- Deactivating is still the same:
$ deactivate- To delete:
$ rmvirtualenv venvOther useful commands¶
lsvirtualenv- List all of the environments.
cdvirtualenv- Navigate into the directory of the currently activated virtual environment,so you can browse its
site-packages, for example. cdsitepackages- Like the above, but directly into
site-packagesdirectory. lssitepackages- Shows contents of
site-packagesdirectory.
virtualenv-burrito¶
Withvirtualenv-burrito, youcan have a working virtualenv + virtualenvwrapper environment in a single command.
