1.. highlight:: none 2 3.. _installing-index: 4 5************************* 6Installing Python Modules 7************************* 8 9:Email: distutils-sig@python.org 10 11As a popular open source development project, Python has an active 12supporting community of contributors and users that also make their software 13available for other Python developers to use under open source license terms. 14 15This allows Python users to share and collaborate effectively, benefiting 16from the solutions others have already created to common (and sometimes 17even rare!) problems, as well as potentially contributing their own 18solutions to the common pool. 19 20This guide covers the installation part of the process. For a guide to 21creating and sharing your own Python projects, refer to the 22`Python packaging user guide`_. 23 24.. _Python Packaging User Guide: https://packaging.python.org/en/latest/tutorials/packaging-projects/ 25 26.. note:: 27 28 For corporate and other institutional users, be aware that many 29 organisations have their own policies around using and contributing to 30 open source software. Please take such policies into account when making 31 use of the distribution and installation tools provided with Python. 32 33 34Key terms 35========= 36 37* ``pip`` is the preferred installer program. Starting with Python 3.4, it 38 is included by default with the Python binary installers. 39* A *virtual environment* is a semi-isolated Python environment that allows 40 packages to be installed for use by a particular application, rather than 41 being installed system wide. 42* ``venv`` is the standard tool for creating virtual environments, and has 43 been part of Python since Python 3.3. Starting with Python 3.4, it 44 defaults to installing ``pip`` into all created virtual environments. 45* ``virtualenv`` is a third party alternative (and predecessor) to 46 ``venv``. It allows virtual environments to be used on versions of 47 Python prior to 3.4, which either don't provide ``venv`` at all, or 48 aren't able to automatically install ``pip`` into created environments. 49* The `Python Package Index <https://pypi.org>`__ is a public 50 repository of open source licensed packages made available for use by 51 other Python users. 52* the `Python Packaging Authority 53 <https://www.pypa.io/>`__ is the group of 54 developers and documentation authors responsible for the maintenance and 55 evolution of the standard packaging tools and the associated metadata and 56 file format standards. They maintain a variety of tools, documentation, 57 and issue trackers on `GitHub <https://github.com/pypa>`__. 58* ``distutils`` is the original build and distribution system first added to 59 the Python standard library in 1998. While direct use of ``distutils`` is 60 being phased out, it still laid the foundation for the current packaging 61 and distribution infrastructure, and it not only remains part of the 62 standard library, but its name lives on in other ways (such as the name 63 of the mailing list used to coordinate Python packaging standards 64 development). 65 66.. versionchanged:: 3.5 67 The use of ``venv`` is now recommended for creating virtual environments. 68 69.. seealso:: 70 71 `Python Packaging User Guide: Creating and using virtual environments 72 <https://packaging.python.org/installing/#creating-virtual-environments>`__ 73 74 75Basic usage 76=========== 77 78The standard packaging tools are all designed to be used from the command 79line. 80 81The following command will install the latest version of a module and its 82dependencies from the Python Package Index:: 83 84 python -m pip install SomePackage 85 86.. note:: 87 88 For POSIX users (including macOS and Linux users), the examples in 89 this guide assume the use of a :term:`virtual environment`. 90 91 For Windows users, the examples in this guide assume that the option to 92 adjust the system PATH environment variable was selected when installing 93 Python. 94 95It's also possible to specify an exact or minimum version directly on the 96command line. When using comparator operators such as ``>``, ``<`` or some other 97special character which get interpreted by shell, the package name and the 98version should be enclosed within double quotes:: 99 100 python -m pip install SomePackage==1.0.4 # specific version 101 python -m pip install "SomePackage>=1.0.4" # minimum version 102 103Normally, if a suitable module is already installed, attempting to install 104it again will have no effect. Upgrading existing modules must be requested 105explicitly:: 106 107 python -m pip install --upgrade SomePackage 108 109More information and resources regarding ``pip`` and its capabilities can be 110found in the `Python Packaging User Guide <https://packaging.python.org>`__. 111 112Creation of virtual environments is done through the :mod:`venv` module. 113Installing packages into an active virtual environment uses the commands shown 114above. 115 116.. seealso:: 117 118 `Python Packaging User Guide: Installing Python Distribution Packages 119 <https://packaging.python.org/installing/>`__ 120 121 122How do I ...? 123============= 124 125These are quick answers or links for some common tasks. 126 127... install ``pip`` in versions of Python prior to Python 3.4? 128-------------------------------------------------------------- 129 130Python only started bundling ``pip`` with Python 3.4. For earlier versions, 131``pip`` needs to be "bootstrapped" as described in the Python Packaging 132User Guide. 133 134.. seealso:: 135 136 `Python Packaging User Guide: Requirements for Installing Packages 137 <https://packaging.python.org/installing/#requirements-for-installing-packages>`__ 138 139 140.. installing-per-user-installation: 141 142... install packages just for the current user? 143----------------------------------------------- 144 145Passing the ``--user`` option to ``python -m pip install`` will install a 146package just for the current user, rather than for all users of the system. 147 148 149... install scientific Python packages? 150--------------------------------------- 151 152A number of scientific Python packages have complex binary dependencies, and 153aren't currently easy to install using ``pip`` directly. At this point in 154time, it will often be easier for users to install these packages by 155`other means <https://packaging.python.org/science/>`__ 156rather than attempting to install them with ``pip``. 157 158.. seealso:: 159 160 `Python Packaging User Guide: Installing Scientific Packages 161 <https://packaging.python.org/science/>`__ 162 163 164... work with multiple versions of Python installed in parallel? 165---------------------------------------------------------------- 166 167On Linux, macOS, and other POSIX systems, use the versioned Python commands 168in combination with the ``-m`` switch to run the appropriate copy of 169``pip``:: 170 171 python2 -m pip install SomePackage # default Python 2 172 python2.7 -m pip install SomePackage # specifically Python 2.7 173 python3 -m pip install SomePackage # default Python 3 174 python3.4 -m pip install SomePackage # specifically Python 3.4 175 176Appropriately versioned ``pip`` commands may also be available. 177 178On Windows, use the ``py`` Python launcher in combination with the ``-m`` 179switch:: 180 181 py -2 -m pip install SomePackage # default Python 2 182 py -2.7 -m pip install SomePackage # specifically Python 2.7 183 py -3 -m pip install SomePackage # default Python 3 184 py -3.4 -m pip install SomePackage # specifically Python 3.4 185 186.. other questions: 187 188 Once the Development & Deployment part of PPUG is fleshed out, some of 189 those sections should be linked from new questions here (most notably, 190 we should have a question about avoiding depending on PyPI that links to 191 https://packaging.python.org/en/latest/mirrors/) 192 193 194Common installation issues 195========================== 196 197Installing into the system Python on Linux 198------------------------------------------ 199 200On Linux systems, a Python installation will typically be included as part 201of the distribution. Installing into this Python installation requires 202root access to the system, and may interfere with the operation of the 203system package manager and other components of the system if a component 204is unexpectedly upgraded using ``pip``. 205 206On such systems, it is often better to use a virtual environment or a 207per-user installation when installing packages with ``pip``. 208 209 210Pip not installed 211----------------- 212 213It is possible that ``pip`` does not get installed by default. One potential fix is:: 214 215 python -m ensurepip --default-pip 216 217There are also additional resources for `installing pip. 218<https://packaging.python.org/en/latest/tutorials/installing-packages/#ensure-pip-setuptools-and-wheel-are-up-to-date>`__ 219 220 221Installing binary extensions 222---------------------------- 223 224Python has typically relied heavily on source based distribution, with end 225users being expected to compile extension modules from source as part of 226the installation process. 227 228With the introduction of support for the binary ``wheel`` format, and the 229ability to publish wheels for at least Windows and macOS through the 230Python Package Index, this problem is expected to diminish over time, 231as users are more regularly able to install pre-built extensions rather 232than needing to build them themselves. 233 234Some of the solutions for installing `scientific software 235<https://packaging.python.org/science/>`__ 236that are not yet available as pre-built ``wheel`` files may also help with 237obtaining other binary extensions without needing to build them locally. 238 239.. seealso:: 240 241 `Python Packaging User Guide: Binary Extensions 242 <https://packaging.python.org/extensions/>`__ 243