Installing packages using pip and virtual environments¶
This guide discusses how to install packages using pip and a virtual environment manager: either venv for Python 3 or virtualenv for Python 2. These are the lowest-level tools for managing Python packages and are recommended if higher-level tools do not suit your needs.
This doc uses the term package to refer to a Distribution Package which is different from an Import Package that which is used to import modules in your Python source code.
Installing pip¶
pip is the reference Python package manager. It’s used to install and update packages. You’ll need to make sure you have the latest version of pip installed.
Debian and most other distributions include a python-pip package; if you want to use the Linux distribution-provided versions of pip, see Installing pip/setuptools/wheel with Linux Package Managers .
You can also install pip yourself to ensure you have the latest version. It’s recommended to use the system pip to bootstrap a user installation of pip:
python3 -m pip install --user --upgrade pip python3 -m pip --version
Afterwards, you should have the latest version of pip installed in your user site:
pip 21.1.3 from $HOME/.local/lib/python3.9/site-packages (python 3.9)
The Python installers for Windows include pip. You can make sure that pip is up-to-date by running:
py -m pip install --upgrade pip py -m pip --version
Afterwards, you should have the latest version of pip:
pip 21.1.3 from c:\python39\lib\site-packages (Python 3.9.4)
Installing virtualenv¶
If you are using Python 3.3 or newer, the venv module is the preferred way to create and manage virtual environments. venv is included in the Python standard library and requires no additional installation. If you are using venv, you may skip this section.
virtualenv is used to manage Python packages for different projects. Using virtualenv allows you to avoid installing Python packages globally which could break system tools or other projects. You can install virtualenv using pip.
python3 -m pip install --user virtualenv
py -m pip install --user virtualenv
Creating a virtual environment¶
venv (for Python 3) and virtualenv (for Python 2) allow you to manage separate package installations for different projects. They essentially allow you to create a “virtual” isolated Python installation and install packages into that virtual installation. When you switch projects, you can simply create a new virtual environment and not have to worry about breaking the packages installed in the other environments. It is always recommended to use a virtual environment while developing Python applications.
To create a virtual environment, go to your project’s directory and run venv. If you are using Python 2, replace venv with virtualenv in the below commands.
python3 -m venv env
py -m venv env
The second argument is the location to create the virtual environment. Generally, you can just create this in your project and call it env .
venv will create a virtual Python installation in the env folder.
You should exclude your virtual environment directory from your version control system using .gitignore or similar.
Activating a virtual environment¶
Before you can start installing or using packages in your virtual environment you’ll need to activate it. Activating a virtual environment will put the virtual environment-specific python and pip executables into your shell’s PATH .
source env/bin/activate .\env\Scripts\activate
You can confirm you’re in the virtual environment by checking the location of your Python interpreter:
Installing Python Modules¶
As a popular open source development project, Python has an active supporting community of contributors and users that also make their software available for other Python developers to use under open source license terms.
This allows Python users to share and collaborate effectively, benefiting from the solutions others have already created to common (and sometimes even rare!) problems, as well as potentially contributing their own solutions to the common pool.
This guide covers the installation part of the process. For a guide to creating and sharing your own Python projects, refer to the Python packaging user guide.
For corporate and other institutional users, be aware that many organisations have their own policies around using and contributing to open source software. Please take such policies into account when making use of the distribution and installation tools provided with Python.
Key terms¶
- pip is the preferred installer program. Starting with Python 3.4, it is included by default with the Python binary installers.
- A virtual environment is a semi-isolated Python environment that allows packages to be installed for use by a particular application, rather than being installed system wide.
- venv is the standard tool for creating virtual environments, and has been part of Python since Python 3.3. Starting with Python 3.4, it defaults to installing pip into all created virtual environments.
- virtualenv is a third party alternative (and predecessor) to venv . It allows virtual environments to be used on versions of Python prior to 3.4, which either don’t provide venv at all, or aren’t able to automatically install pip into created environments.
- The Python Package Index is a public repository of open source licensed packages made available for use by other Python users.
- the Python Packaging Authority is the group of developers and documentation authors responsible for the maintenance and evolution of the standard packaging tools and the associated metadata and file format standards. They maintain a variety of tools, documentation, and issue trackers on both GitHub and Bitbucket.
- distutils is the original build and distribution system first added to the Python standard library in 1998. While direct use of distutils is being phased out, it still laid the foundation for the current packaging and distribution infrastructure, and it not only remains part of the standard library, but its name lives on in other ways (such as the name of the mailing list used to coordinate Python packaging standards development).
Changed in version 3.5: The use of venv is now recommended for creating virtual environments.
Basic usage¶
The standard packaging tools are all designed to be used from the command line.
The following command will install the latest version of a module and its dependencies from the Python Package Index:
python -m pip install SomePackage
For POSIX users (including macOS and Linux users), the examples in this guide assume the use of a virtual environment .
For Windows users, the examples in this guide assume that the option to adjust the system PATH environment variable was selected when installing Python.
It’s also possible to specify an exact or minimum version directly on the command line. When using comparator operators such as > , < or some other special character which get interpreted by shell, the package name and the version should be enclosed within double quotes:
python -m pip install SomePackage==1.0.4 # specific version python -m pip install "SomePackage>=1.0.4" # minimum version
Normally, if a suitable module is already installed, attempting to install it again will have no effect. Upgrading existing modules must be requested explicitly:
python -m pip install --upgrade SomePackage
More information and resources regarding pip and its capabilities can be found in the Python Packaging User Guide.
Creation of virtual environments is done through the venv module. Installing packages into an active virtual environment uses the commands shown above.
How do I …?¶
These are quick answers or links for some common tasks.
… install pip in versions of Python prior to Python 3.4?¶
Python only started bundling pip with Python 3.4. For earlier versions, pip needs to be “bootstrapped” as described in the Python Packaging User Guide.
… install packages just for the current user?¶
Passing the —user option to python -m pip install will install a package just for the current user, rather than for all users of the system.
… install scientific Python packages?¶
A number of scientific Python packages have complex binary dependencies, and aren’t currently easy to install using pip directly. At this point in time, it will often be easier for users to install these packages by other means rather than attempting to install them with pip .
… work with multiple versions of Python installed in parallel?¶
On Linux, macOS, and other POSIX systems, use the versioned Python commands in combination with the -m switch to run the appropriate copy of pip :
python2 -m pip install SomePackage # default Python 2 python2.7 -m pip install SomePackage # specifically Python 2.7 python3 -m pip install SomePackage # default Python 3 python3.4 -m pip install SomePackage # specifically Python 3.4
Appropriately versioned pip commands may also be available.
On Windows, use the py Python launcher in combination with the -m switch:
py -2 -m pip install SomePackage # default Python 2 py -2.7 -m pip install SomePackage # specifically Python 2.7 py -3 -m pip install SomePackage # default Python 3 py -3.4 -m pip install SomePackage # specifically Python 3.4
Common installation issues¶
Installing into the system Python on Linux¶
On Linux systems, a Python installation will typically be included as part of the distribution. Installing into this Python installation requires root access to the system, and may interfere with the operation of the system package manager and other components of the system if a component is unexpectedly upgraded using pip .
On such systems, it is often better to use a virtual environment or a per-user installation when installing packages with pip .
Pip not installed¶
It is possible that pip does not get installed by default. One potential fix is:
python -m ensurepip --default-pip
There are also additional resources for installing pip.
Installing binary extensions¶
Python has typically relied heavily on source based distribution, with end users being expected to compile extension modules from source as part of the installation process.
With the introduction of support for the binary wheel format, and the ability to publish wheels for at least Windows and macOS through the Python Package Index, this problem is expected to diminish over time, as users are more regularly able to install pre-built extensions rather than needing to build them themselves.
Some of the solutions for installing scientific software that are not yet available as pre-built wheel files may also help with obtaining other binary extensions without needing to build them locally.
Installing Packages¶
This section covers the basics of how to install Python packages .
It’s important to note that the term “package” in this context is being used to describe a bundle of software to be installed (i.e. as a synonym for a distribution ). It does not to refer to the kind of package that you import in your Python source code (i.e. a container of modules). It is common in the Python community to refer to a distribution using the term “package”. Using the term “distribution” is often not preferred, because it can easily be confused with a Linux distribution, or another larger software distribution like Python itself.
- Requirements for Installing Packages
- Ensure you can run Python from the command line
- Ensure you can run pip from the command line
- Ensure pip, setuptools, and wheel are up to date
- Optionally, create a virtual environment
Requirements for Installing Packages¶
This section describes the steps to follow before installing other Python packages.
Ensure you can run Python from the command line¶
Before you go any further, make sure you have Python and that the expected version is available from your command line. You can check this by running:
python3 --version
py --version
You should get some output like Python 3.6.3 . If you do not have Python, please install the latest 3.x version from python.org or refer to the Installing Python section of the Hitchhiker’s Guide to Python.
If you’re a newcomer and you get an error like this:
>>> python3 --version Traceback (most recent call last): File "", line 1, in NameError: name 'python3' is not defined
It’s because this command and other suggested commands in this tutorial are 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.
If you’re using an enhanced shell like IPython or the Jupyter notebook, you can run system commands like those in this tutorial by prefacing them with a ! character:
In [1]: import sys ! --version Python 3.6.3
It’s recommended to write rather than plain python in order to ensure that commands are run in the Python installation matching the currently running notebook (which may not be the same Python installation that the python command refers to).
Due to the way most Linux distributions are handling the Python 3 migration, Linux users using the system Python without creating a virtual environment first should replace the python command in this tutorial with python3 and the python -m pip command with python3 -m pip —user . Do not run any of the commands in this tutorial with sudo : if you get a permissions error, come back to the section on creating virtual environments, set one up, and then continue with the tutorial as written.
Ensure you can run pip from the command line¶
Additionally, you’ll need to make sure you have pip available. You can check this by running:
python3 -m pip --version
py -m pip --version
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 separately, see Installing pip/setuptools/wheel with Linux Package Managers .
If pip isn’t already installed, then first try to bootstrap it from the standard library:
python3 -m ensurepip --default-pip
py -m ensurepip --default-pip
If that still doesn’t allow you to run python -m pip :
- Securely Download get-pip.py1
- Run python get-pip.py . 2 This will install or upgrade pip. Additionally, it will install setuptools and wheel if they’re not installed already.
Warning Be cautious if you’re using a Python install that’s managed by your operating system or another package manager. get-pip.py does not coordinate with those tools, and may leave your system in an inconsistent state. You can use python get-pip.py —prefix=/usr/local/ to install in /usr/local which is designed for locally-installed software.
Ensure pip, setuptools, and wheel are up to date¶
While pip alone is sufficient to install from pre-built binary archives, up to date copies of the setuptools and wheel projects are useful to ensure you can also install from source archives:
python3 -m pip install --upgrade pip setuptools wheel
py -m pip install --upgrade pip setuptools wheel
Optionally, create a virtual environment¶
See section below for details, but here’s the basic venv 3 command to use on a typical Linux system:
python3 -m venv tutorial_env source tutorial_env/bin/activatepy -m venv tutorial_env tutorial_env\Scripts\activate
This will create a new virtual environment in the tutorial_env subdirectory, and configure the current shell to use it as the default python environment.
Creating Virtual Environments¶
Python “Virtual Environments” allow Python packages to be installed in an isolated location for a particular application, rather than being installed globally. If you are looking to safely install global command line tools, see Installing stand alone command line tools .
Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python3.6/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.
Or more generally, what if you want to install an application and leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application.
Also, what if you can’t install packages into the global site-packages directory? For instance, on a shared host.
In all these cases, virtual environments can help you. They have their own installation directories and they don’t share libraries with other virtual environments.
Currently, there are two common tools for creating Python virtual environments:
- venv is available by default in Python 3.3 and later, and installs pip and setuptools into created virtual environments in Python 3.4 and later.
- virtualenv needs to be installed separately, but supports Python 2.7+ and Python 3.3+, and pip , setuptools and wheel are always installed into created virtual environments by default (regardless of Python version).
The basic usage is like so:
python3 -m venv source /bin/activateПри подготовке материала использовались источники:
https://packaging.python.org/en/latest/guides/installing-using-pip-and-virtual-environments/
https://docs.python.org/3/installing/index.html
https://packaging.python.org/en/latest/tutorials/installing-packages/