Instalacja modułów Pythona

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distutils-sig@python.org

Python, jako popularny projekt open source, cieszy się aktywnym wsparciem społeczności współtwórców i użytkowników, którzy udostępniają tworzone przez siebie oprogramowanie innym deweloperom Pythona w ramach licencji open source.

Dzięki temu użytkownicy Pythpa mogą efektywnie korzystać się i współpracować korzystając z rozwiązań stworzonych wcześniej w odpowiedzi na popularne problemy (a czasami bardzo rzadkie!), oraz udostępniać własne rozwiązania całej społeczności.

Ta część przewodnika dotyczy procesu instalacji. O tworzeniu i dzieleniu się własnymi projektami w Pythonie przeczytasz więcej w Przewodniku dystrybucji.

Informacja

Użytkownicy związani z korporacjami i innymi instytucjami powinni zwrócić uwagę, że wiele organizacji ma własne zasady dotyczące korzystania z oprogramowania i udziału w projektach open source. Należy brać takie zasady pod uwagę korzystając z narzędzi instalacyjnych i dystrybucyjnych Pythona.

Główne pojęcia

  • pip jest preferowanym instalatorem. Od wersji Pythona 3.4 jest domyślnie dołączony do instalatorów binarnych.

  • Środowisko wirtualne jest częściowo wyizolowanym środowiskiem Pythona instalowanym na potrzeby poszczególnych aplikacji a nie całego sytemu.

  • venv jest strandardowym narzędziem do tworzenia środowisk wirtualnych. Jest częścią Pythona od wersji 3.3, a od 3.4 domyślnie instaluje pip we wszystkich tworzonych środowiskach wirtualnych.

  • virtualenv to zewnętrzne (i starsze) rozwiązania alternatywne wobec venv. Pozwala korzystać ze środowisk wirtualnych w wesjach Pythona wcześniejszych niż 3.4, które albo nie zapewniają venv, albo nie są w stanie automatycznie zainstalować pip w tworzonych środowiskach.

  • The Python Packaging 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).

Zmienione w wersji 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 Packaging Index:

python -m pip install SomePackage

Informacja

For POSIX users (including Mac OS X 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, Mac OS X, 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 Mac OS X through the Python Packaging 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.