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 like 3.6.2
. If you do not have Python, pleaseinstall the latest 3.x version from python.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>", line 1, in <module>NameError: name 'python' is not defined
It’s because this command is intended to be run in a shell (also calleda terminal or console). 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 have pip available. You cancheck this by running:
$ pip --version
If you installed Python from source, with an installer from python.org, orvia Homebrew you should already have pip. If you’re on Linux and installedusing your OS package manager, you may have to install pip separately.
Installing Pipenv¶
Pipenv is a dependency manager for Python projects. If you’re familiarwith Node.js’ npm or Ruby’s bundler, it is similar in spirit to thosetools. While pip can install Python packages, Pipenv is recommended asit’s a higher-level tool that simplifies dependency management for common usecases.
Use pip
to install Pipenv:
$ pip install --user pipenv
Note
This does a user installation to prevent breaking any system-widepackages. 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 runningpython -m site --user-base
and adding bin
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 your PATH
. You can set your PATH
permanently bymodifying ~/.profile.
On Windows you can find the user base binary directory by runningpy -m site --user-site
and replacing site-packages
withScripts
. For example, this could returnC:\Users\Username\AppData\Roaming\Python36\site-packages
so you wouldneed to set your PATH
to includeC:\Users\Username\AppData\Roaming\Python36\Scripts
. You can set youruser PATH
permanently in the Control Panel. You may need to logout for the PATH
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 project_folder$ pipenv install requests
Pipenv will install the excellent Requests library and create a Pipfile
for you in your project’s directory. The Pipfile 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 simple main.py
file touse it:
import requestsresponse = requests.get('https://httpbin.org/ip')print('Your IP is {0}'.format(response.json()['origin']))
Then you can run this script using pipenv run
:
$ pipenv run python main.py
You should get output similar to this:
Your IP is 8.8.8.8
Using $ pipenv run
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 $ pipenv shell
.
Next steps¶
Congratulations, you now know how to install and use Python packages! ✨ 🍰 ✨
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 virtualenv
Test your installation:
$ virtualenv --version
Basic Usage¶
- Create a virtual environment for a project:
$ cd project_folder$ virtualenv venv
virtualenv venv
will create a folder in the current directory which willcontain the Python executable files, and a copy of the pip
library which youcan use to install other packages. The name of the virtual environment (in thiscase, it was venv
) can be anything; omitting the name will place the filesin the current directory instead.
Note
‘venv’ is the general convention used globally. As it is readily available in ignore files (eg: .gitignore’)
This creates a copy of Python in whichever directory you ran the command in,placing it in a folder named venv
.
You can also use the Python interpreter of your choice (likepython2.7
).
$ virtualenv -p /usr/bin/python2.7 venv
or change the interpreter globally with an env variable in ~/.bashrc
:
$ export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python2.7
- To begin using the virtual environment, it needs to be activated:
$ source venv/bin/activate
The name of the current virtual environment will now appear on the left ofthe prompt (e.g. (venv)Your-Computer:project_folder UserName$
) to let you knowthat it’s active. From now on, any package that you install using pip will beplaced in the venv
folder, isolated from the global Python installation.
For Windows, the same command mentioned in step 1 can be used to create a virtual environment. However, activating the environment requires a slightly different command.
Assuming that you are in your project directory:
C:\Users\SomeUser\project_folder> venv\Scripts\activate
Install packages using the pip
command:
$ pip install requests
- If you are done working in the virtual environment for the moment, you candeactivate it:
$ deactivate
This 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 be rm -rf venv
.)
After a while, though, you might end up with a lot of virtual environmentslittered across your system, and it’s possible you’ll forget their names orwhere they were placed.
Note
Python has included venv module from version 3.3. For more details: venv.
Other Notes¶
Running virtualenv
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 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:
$ pip freeze > requirements.txt
This will create a requirements.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.txt
This 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 (see Version 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 sure virtualenv is already installed):
$ pip install virtualenvwrapper$ export WORKON_HOME=~/Envs$ source /usr/local/bin/virtualenvwrapper.sh
(Full virtualenvwrapper install instructions.)
For Windows, you can use the virtualenvwrapper-win.
To install (make sure virtualenv is already installed):
$ pip install virtualenvwrapper-win
In Windows, the default path for WORKON_HOME is %USERPROFILE%\Envs
Basic Usage¶
- Create a virtual environment:
$ mkvirtualenv project_folder
This creates the project_folder
folder inside ~/Envs
.
- Work on a virtual environment:
$ workon project_folder
Alternatively, you can make a project, which creates the virtual environment,and also a project directory inside $WORKON_HOME
, which is cd
-ed intowhen you workon project_folder
.
$ mkproject project_folder
virtualenvwrapper 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 venv
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
site-packages
, for example. cdsitepackages
- Like the above, but directly into
site-packages
directory. lssitepackages
- Shows contents of
site-packages
directory.
virtualenv-burrito¶
With virtualenv-burrito, youcan have a working virtualenv + virtualenvwrapper environment in a single command.
direnv¶
When you cd
into a directory containing a .env
, direnvautomagically activates the environment.
Install it on Mac OS X using brew
:
$ brew install direnv
On Linux follow the instructions at direnv.net