Download the latest version of Python
All Python releases are Open Source. Historically, most, but not all, Python releases have also been GPL-compatible. The Licenses page details GPL-compatibility and Terms and Conditions.
Sources
For most Unix systems, you must download and compile the source code. The same source code archive can also be used to build the Windows and Mac versions, and is the starting point for ports to all other platforms.
Download the latest Python 3 source.
Alternative Implementations
This site hosts the «traditional» implementation of Python (nicknamed CPython). A number of alternative implementations are available as well.
History
Python was created in the early 1990s by Guido van Rossum at Stichting Mathematisch Centrum in the Netherlands as a successor of a language called ABC. Guido remains Python’s principal author, although it includes many contributions from others.
Release Schedules
See Status of Python Versions for all an overview of all versions, including unsupported.
Information about specific ports, and developer info
OpenPGP Public Keys
Source and binary executables are signed by the release manager or binary builder using their OpenPGP key. Release files for currently supported releases are signed by the following:
- Thomas Wouters (3.12.x and 3.13.x source files and tags) (key id: A821E680E5FA6305) (key id: 64E628F8D684696D) (key id: FC62 4643 4870 34E5) (key id: B269 95E3 1025 0568) (key ids: 2D34 7EA6 AA65 421D, FB99 2128 6F5E 1540, and Apple Developer ID DJ3H93M7VJ)
- Larry Hastings (3.5.x source files and tags) (key id: 3A5C A953 F73C 700D) (key id: 04C3 67C2 18AD D4FF and A4135B38)
Release files for older releases which have now reached end-of-life may have been signed by one of the following:
- Anthony Baxter (key id: 0EDD C5F2 6A45 C816)
- Georg Brandl (key id: 0A5B 1018 3658 0288)
- Martin v. Löwis (key id: 6AF0 53F0 7D9D C8D2)
- Ronald Oussoren (key id: C9BE 28DE E6DF 025C) (key ids: 126E B563 A74B 06BF, D986 6941 EA5B BD71, and ED9D77D5)
You can import a person’s public keys from a public keyserver network server you trust by running a command like:
or, in many cases, public keys can also be found at keybase.io. On the version-specific download pages, you should see a link to both the downloadable file and a detached signature file. To verify the authenticity of the download, grab both files and then run this command:
Note that you must use the name of the signature file, and you should use the one that’s appropriate to the download you’re verifying.
- (These instructions are geared to GnuPG and Unix command-line users.)
Other Useful Items
- Looking for 3rd party Python modules? The Package Index has many of them.
- You can view the standard documentation online, or you can download it in HTML, PostScript, PDF and other formats. See the main Documentation page.
- Information on tools for unpacking archive files provided on python.org is available.
- Tip: even if you download a ready-made binary for your platform, it makes sense to also download the source. This lets you browse the standard library (the subdirectory Lib) and the standard collections of demos (Demo) and tools (Tools) that come with it. There’s a lot you can learn from the source!
- There is also a collection of Emacs packages that the Emacsing Pythoneer might find useful. This includes major modes for editing Python, C, C++, Java, etc., Python debugger interfaces and more. Most packages are compatible with Emacs and XEmacs.
Want to contribute?
Want to contribute? See the Python Developer’s Guide to learn about how Python development is managed.
Как запустить Python офлайн и онлайн: руководство для новичка
Python — самый популярный язык программирования, на котором разрабатывают ИИ, игры и сложные системы. Разбираемся с его установкой.
Иллюстрация: Skillbox Media
Python — это высокоуровневый язык программирования общего назначения с минималистичным и простым в освоении синтаксисом. Он был создан под влиянием языка ABC, который изначально задумывался как обучающий и над которым ранее работал автор Python Гвидо ван Россум.
К сожалению, не все ОС содержат Python по умолчанию. В таких случаях, чтобы начать программировать на языке, его придётся установить. В этой статье мы расскажем, как это сделать.
Гайд по установке Python:
Какую версию Python выбрать
Вообще, для решения простых задач или знакомства с языком хватит и онлайн-интерпретатора. Это сервис, который позволяет писать и запускать код прямо в браузере, ничего не скачивая. Самые популярные онлайн-интерпретаторы — Replit, Programiz и Online Python.
Это хороший инструмент, но только для написания простых программ. Там сложно тестировать приложения, полноценно работать с файлами и использовать продвинутые возможности языка.
Для полноценной разработки всё-таки нужно будет установить Python на компьютер. Но, поверьте, оно того стоит: вы сможете легко подключать сторонние библиотеки, использовать утилиты и создавать сложные проекты.
Выбор версии языка — тоже важный этап. Очевидно, что в новых версиях больше интересных фишек и, как правило, меньше багов — поэтому для собственных проектов лучше скачивать самый свежий дистрибутив. На момент написания статьи это Python 3.11.2.
Однако для поддержки старых проектов, которые не могут переехать на Python 3, придётся скачивать Python 2 и разбираться в различиях версий. Поэтому даже в 2023 году в вакансиях среди требований можно найти «уверенное знание Python 2.7».
В состав базовой версии Python входят следующие компоненты:
- IDLE — простая среда разработки Python-программ;
- документация — инструкция по использованию Python;
- стандартная библиотека — набор функций, которые упрощают работу с числами, файлами, API сторонних сервисов и так далее;
- пакетный менеджер PIP — утилита для скачивания и установки библиотек, фреймворков и других пакетов, расширяющих функциональность Python;
- стандартный набор тестов — чтобы проверять надёжность программы;
- Python Launcher — приложение для запуска программ с расширением .py.
Этого набора вполне хватит, чтобы начать изучение языка и писать простые программы.
Как установить Python на Windows, Linux и macOS
Перед установкой убедитесь, что ваш компьютер удовлетворяет системным требованиям:
- 64- или 32-разрядный процессор на архитектуре Intel или AMD;
- 2 ГБ оперативной памяти, желательно 4 ГБ;
- 5 ГБ свободного места в памяти компьютера;
- версия операционной системы: не ниже Windows 7, macOS X 10.11, Red Hat Enterprise Linux 6/7.
Дистрибутивы Python есть для всех популярных операционных систем, они перечислены на официальном сайте python.org. По большому счёту, не так важно, какую конкретно версию Python вы скачаете, — главное, чтобы её номер начинался с цифры 3.
Установка в Windows 10
Скачайте установочный файл, нажав на жёлтую кнопку Download Python, и запустите его.
Выберите путь установки и поставьте обе галочки: во втором пункте мы указываем, что нужно добавить Python в переменную окружения PATH — это позволит вызывать его из любой директории. Затем выбираем «Установка для всех пользователей» (Install for all users), нажимаем Install Now и разрешаем приложению вносить изменения:
Когда всё установится, вы увидите окно завершения инсталляции:
Теперь проверим, что Python действительно установлен. Для этого откроем окно «Выполнить» сочетанием клавиш Win + R и введём cmd:
Откроется командная строка. Введите в ней команду py или python, чтобы запустить интерпретатор. На экране появится примерно такое сообщение:
Оно означает, что Python установлен на ваш компьютер и работает.
Как установить Python на Windows 7 или более раннюю версию
Если у вас более ранняя версия Windows, процесс установки Python ничем не отличается, кроме того, что некоторые версии языка не поддерживаются на старых операционных системах. Узнать, подходит ли версия Python вашей ОС, можно в примечаниях на странице скачивания:
Установка в Linux
Python входит в состав большинства дистрибутивов Linux. Чтобы это проверить, введите в терминале следующую команду:
В окне должен появиться номер версии языка. Если этого не произошло, нужно установить Python с помощью пакетного менеджера.
В Ubuntu 16.10 это делается так:
Утилита попросит вас ввести пароль и после ввода начнёт установку.
Однако, если вы хотите поставить более свежую версию Python, для установки нужно использовать репозиторий deadsnakes PPA:
В Fedora Linux процесс установки похожий, но используется другая команда:
Ещё можно самостоятельно собрать Python из исходников, которые лежат на сайте Python. Но это очень сложный и мучительный процесс, поэтому останавливаться на нём мы не будем.
macOS
С давних времён MacBook и iMac выпускались с предустановленным Python 2.7. Правда, начиная с версии 12.3 разработчики «яблочной» ОС отказались от этой традиции.
Чтобы проверить, установлен ли Python, откройте командную строку и введите следующую команду:
В любом случае лучше установить последнюю версию Python — найти её можно на официальном сайте.
Нажмите жёлтую кнопку Download Python 3.11.2, и пакет начнёт скачиваться:
Когда загрузка завершится, откройте его:
Согласитесь со всеми пунктами и переходите к установке. Вас попросят ввести пароль, а после — начнётся установка, по окончании которой вы увидите такое окно:
Нажмите Close и откройте терминал, чтобы проверить версию Python:
Должно быть выведено сообщение Python 3.11.2.
Как установить Python для data science
Дата-сайентисты используют свои библиотеки для работы — например, NumPy и Pandas. Их можно устанавливать по отдельности, а можно скачать готовую сборку со всеми библиотеками.
Самый популярный способ — использовать дистрибутив Anaconda. Он бесплатный и легко устанавливаемый, а также доступен для всех операционных систем. Мы покажем, как установить его на macOS.
Нажмите на кнопку Download, чтобы начать скачивание:
Затем откройте установщик, согласитесь со всеми пунктами и выберите место для установки.
Чтобы убедиться, что Python установлен, откройте консоль и введите команду python3 — должен запуститься интерпретатор Python, в котором можно писать код. Выглядит это примерно так:
Теперь, чтобы использовать одну из библиотек для data science, нужно всего лишь импортировать её в Python-файле:
А чтобы проверить, работает ли библиотека, достаточно запустить файл, в котором вы её подключили. Если библиотека не подключилась, то интерпретатор выдаст сообщение об ошибке.
Если хотите узнать больше об инструментах для анализа данных, советуем прочитать нашу статью о библиотеке NumPy.
Как начать работать с Python
После того как мы установили Python, пора написать пару строк кода. Вы можете использовать любую IDE (в том числе IDLE), редактор кода или даже «Блокнот».
Создадим файл program.py на рабочем столе. В нём мы вызовем всего одну функцию, которая выведет на экран текстовое сообщение:
Запустим программу командой py или python в командной строке, прописав полный путь до файла program.py. Например, если он лежит на рабочем столе, запустить его можно так:
Мы передали код интерпретатору, который обработал его и вывел сообщение на экран. Всё получилось!
Чтобы узнать, как самостоятельно изучать программирование на Python, советуем прочитать наше руководство для новичков.
Как подключить Python к VS Code
VS Code — это удобный редактор кода, который поддерживает десятки языков программирования и плагинов. По популярности VS Code сильно опережает аналоги, поэтому будет полезно разобраться, как установить Python туда.
Сначала нужно найти плагин для языка. Откройте вкладку Extensions («Расширения») и введите в поиске следующую строку:
В появившемся списке найдите Python и нажмите Install.
Теперь нужно включить подсветку кода. Для этого установите плагин Magic Python — найти его можно в том же поиске, введя команду ext: py3. Чтобы всё заработало, перезапустите VS Code и создайте файл с расширением .py. Когда редактор спросит, на каком языке вы собираетесь программировать, — выберите Python. Готово!
Как установить PyCharm
Хоть VS Code является самым популярным редактором кода, многие программисты предпочитают специализированные IDE, заточенные именно под разработку на Python. Абсолютный фаворит здесь — PyCharm, в состав которой уже входит Python.
Чтобы установить PyCharm, зайдите на сайт JetBrains и нажмите кнопку Download:
Вам предложат выбрать операционную систему и версию среды разработки: Professional и Community. Community — это бесплатная версия, в которой отсутствует поддержка некоторых функций и фреймворков, например Django. Но на первых порах её вполне хватит, поэтому выбираем её:
Скачать Python 3
Большое количество библиотек, созданных для Python, делают его удобным для программирования приложений, игр, интернет-разработок, систем управления базами данных, сетевых решений.
Python предоставляет широкие возможности для образования и научных применений. Используется для программирования роботов. Является удобным инструментом, применяемым для создания систем искусственного интеллекта, машинного обучения, распознавания образов, программирования нейронных сетей.
Python распространяется свободно, даже для коммерческого использования.
О том, как обзавестись этим языком программирования на своем компьютере, читайте на странице «Как установить Python?».
Python 3.9.7
Дата релиза: 30 августа, 2021
Размер: 27 Mb для Windows, 29 Mb для macOS
Python 3.8.6
Дата релиза: 24 сентября, 2020
Размер: 27 Mb для Windows, 29 Mb для macOS
Python 3.4.3
Дата релиза: 25 февраля 2015
Размер: 25 Mb
3. Using Python on Windows¶
This document aims to give an overview of Windows-specific behaviour you should know about when using Python on Microsoft Windows.
3.1. Installing Python¶
Unlike most Unix systems and services, Windows does not include a system supported installation of Python. To make Python available, the CPython team has compiled Windows installers (MSI packages) with every release for many years. These installers are primarily intended to add a per-user installation of Python, with the core interpreter and library being used by a single user. The installer is also able to install for all users of a single machine, and a separate ZIP file is available for application-local distributions.
3.1.1. Supported Versions¶
As specified in PEP 11, a Python release only supports a Windows platform while Microsoft considers the platform under extended support. This means that Python 3.7 supports Windows Vista and newer. If you require Windows XP support then please install Python 3.4.
3.1.2. Installation Steps¶
Four Python 3.7 installers are available for download — two each for the 32-bit and 64-bit versions of the interpreter. The web installer is a small initial download, and it will automatically download the required components as necessary. The offline installer includes the components necessary for a default installation and only requires an internet connection for optional features. See Installing Without Downloading for other ways to avoid downloading during installation.
After starting the installer, one of two options may be selected:
If you select “Install Now”:
- You will not need to be an administrator (unless a system update for the C Runtime Library is required or you install the Python Launcher for Windows for all users)
- Python will be installed into your user directory
- The Python Launcher for Windows will be installed according to the option at the bottom of the first page
- The standard library, test suite, launcher and pip will be installed
- If selected, the install directory will be added to your PATH
- Shortcuts will only be visible for the current user
Selecting “Customize installation” will allow you to select the features to install, the installation location and other options or post-install actions. To install debugging symbols or binaries, you will need to use this option.
To perform an all-users installation, you should select “Customize installation”. In this case:
- You may be required to provide administrative credentials or approval
- Python will be installed into the Program Files directory
- The Python Launcher for Windows will be installed into the Windows directory
- Optional features may be selected during installation
- The standard library can be pre-compiled to bytecode
- If selected, the install directory will be added to the system PATH
- Shortcuts are available for all users
3.1.3. Removing the MAX_PATH Limitation¶
Windows historically has limited path lengths to 260 characters. This meant that paths longer than this would not resolve and errors would result.
In the latest versions of Windows, this limitation can be expanded to approximately 32,000 characters. Your administrator will need to activate the “Enable Win32 long paths” group policy, or set the registry value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem@LongPathsEnabled to 1 .
This allows the open() function, the os module and most other path functionality to accept and return paths longer than 260 characters when using strings. (Use of bytes as paths is deprecated on Windows, and this feature is not available when using bytes.)
After changing the above option, no further configuration is required.
Changed in version 3.6: Support for long paths was enabled in Python.
3.1.4. Installing Without UI¶
All of the options available in the installer UI can also be specified from the command line, allowing scripted installers to replicate an installation on many machines without user interaction. These options may also be set without suppressing the UI in order to change some of the defaults.
To completely hide the installer UI and install Python silently, pass the /quiet option. To skip past the user interaction but still display progress and errors, pass the /passive option. The /uninstall option may be passed to immediately begin removing Python — no prompt will be displayed.
All other options are passed as name=value , where the value is usually 0 to disable a feature, 1 to enable a feature, or a path. The full list of available options is shown below.
| Name | Description | Default |
|---|---|---|
| InstallAllUsers | Perform a system-wide installation. | 0 |
| TargetDir | The installation directory | Selected based on InstallAllUsers |
| DefaultAllUsersTargetDir | The default installation directory for all-user installs | %ProgramFiles%\Python X.Y or %ProgramFiles(x86)%\Python X.Y |
| DefaultJustForMeTargetDir | The default install directory for just-for-me installs | %LocalAppData%\Programs\PythonXY or %LocalAppData%\Programs\PythonXY-32 |
| DefaultCustomTargetDir | The default custom install directory displayed in the UI | (empty) |
| AssociateFiles | Create file associations if the launcher is also installed. | 1 |
| CompileAll | Compile all .py files to .pyc . | 0 |
| PrependPath | Add install and Scripts directories tho PATH and .PY to PATHEXT | 0 |
| Shortcuts | Create shortcuts for the interpreter, documentation and IDLE if installed. | 1 |
| Include_doc | Install Python manual | 1 |
| Include_debug | Install debug binaries | 0 |
| Include_dev | Install developer headers and libraries | 1 |
| Include_exe | Install python.exe and related files | 1 |
| Include_launcher | Install Python Launcher for Windows . | 1 |
| InstallLauncherAllUsers | Installs Python Launcher for Windows for all users. | 1 |
| Include_lib | Install standard library and extension modules | 1 |
| Include_pip | Install bundled pip and setuptools | 1 |
| Include_symbols | Install debugging symbols ( * .pdb) | 0 |
| Include_tcltk | Install Tcl/Tk support and IDLE | 1 |
| Include_test | Install standard library test suite | 1 |
| Include_tools | Install utility scripts | 1 |
| LauncherOnly | Only installs the launcher. This will override most other options. | 0 |
| SimpleInstall | Disable most install UI | 0 |
| SimpleInstallDescription | A custom message to display when the simplified install UI is used. | (empty) |
For example, to silently install a default, system-wide Python installation, you could use the following command (from an elevated command prompt):
To allow users to easily install a personal copy of Python without the test suite, you could provide a shortcut with the following command. This will display a simplified initial page and disallow customization:
(Note that omitting the launcher also omits file associations, and is only recommended for per-user installs when there is also a system-wide installation that included the launcher.)
The options listed above can also be provided in a file named unattend.xml alongside the executable. This file specifies a list of options and values. When a value is provided as an attribute, it will be converted to a number if possible. Values provided as element text are always left as strings. This example file sets the same options and the previous example:
3.1.5. Installing Without Downloading¶
As some features of Python are not included in the initial installer download, selecting those features may require an internet connection. To avoid this need, all possible components may be downloaded on-demand to create a complete layout that will no longer require an internet connection regardless of the selected features. Note that this download may be bigger than required, but where a large number of installations are going to be performed it is very useful to have a locally cached copy.
Execute the following command from Command Prompt to download all possible required files. Remember to substitute python-3.6.0.exe for the actual name of your installer, and to create layouts in their own directories to avoid collisions between files with the same name.
You may also specify the /quiet option to hide the progress display.
3.1.6. Modifying an install¶
Once Python has been installed, you can add or remove features through the Programs and Features tool that is part of Windows. Select the Python entry and choose “Uninstall/Change” to open the installer in maintenance mode.
“Modify” allows you to add or remove features by modifying the checkboxes — unchanged checkboxes will not install or remove anything. Some options cannot be changed in this mode, such as the install directory; to modify these, you will need to remove and then reinstall Python completely.
“Repair” will verify all the files that should be installed using the current settings and replace any that have been removed or modified.
“Uninstall” will remove Python entirely, with the exception of the Python Launcher for Windows , which has its own entry in Programs and Features.
3.1.7. Other Platforms¶
With ongoing development of Python, some platforms that used to be supported earlier are no longer supported (due to the lack of users or developers). Check PEP 11 for details on all unsupported platforms.
-
is still supported.
- The Cygwin installer offers to install the Python interpreter as well (cf. Cygwin package source, Maintainer releases)
See Python for Windows for detailed information about platforms with pre-compiled installers.
3.2. Alternative bundles¶
Besides the standard CPython distribution, there are modified packages including additional functionality. The following is a list of popular versions and their key features:
ActivePython Installer with multi-platform compatibility, documentation, PyWin32 Anaconda Popular scientific modules (such as numpy, scipy and pandas) and the conda package manager. Canopy A “comprehensive Python analysis environment” with editors and other development tools. WinPython Windows-specific distribution with prebuilt scientific packages and tools for building packages.
Note that these packages may not include the latest versions of Python or other libraries, and are not maintained or supported by the core Python team.
3.3. Configuring Python¶
To run Python conveniently from a command prompt, you might consider changing some default environment variables in Windows. While the installer provides an option to configure the PATH and PATHEXT variables for you, this is only reliable for a single, system-wide installation. If you regularly use multiple versions of Python, consider using the Python Launcher for Windows .
3.3.1. Excursus: Setting environment variables¶
Windows allows environment variables to be configured permanently at both the User level and the System level, or temporarily in a command prompt.
To temporarily set environment variables, open Command Prompt and use the set command:
These changes will apply to any further commands executed in that console, and will be inherited by any applications started from the console.
Including the variable name within percent signs will expand to the existing value, allowing you to add your new value at either the start or the end. Modifying PATH by adding the directory containing python.exe to the start is a common way to ensure the correct version of Python is launched.
To permanently modify the default environment variables, click Start and search for ‘edit environment variables’, or open System properties, Advanced system settings and click the Environment Variables button. In this dialog, you can add or modify User and System variables. To change System variables, you need non-restricted access to your machine (i.e. Administrator rights).
Windows will concatenate User variables after System variables, which may cause unexpected results when modifying PATH .
The PYTHONPATH variable is used by all versions of Python 2 and Python 3, so you should not permanently configure this variable unless it only includes code that is compatible with all of your installed Python versions.
https://support.microsoft.com/kb/100843 Environment variables in Windows NT https://technet.microsoft.com/en-us/library/cc754250.aspx The SET command, for temporarily modifying environment variables https://technet.microsoft.com/en-us/library/cc755104.aspx The SETX command, for permanently modifying environment variables https://support.microsoft.com/kb/310519 How To Manage Environment Variables in Windows XP https://www.chem.gla.ac.uk/
louis/software/faq/q1.html Setting Environment variables, Louis J. Farrugia
3.3.2. Finding the Python executable¶
Changed in version 3.5.
Besides using the automatically created start menu entry for the Python interpreter, you might want to start Python in the command prompt. The installer has an option to set that up for you.
On the first page of the installer, an option labelled “Add Python to PATH” may be selected to have the installer add the install location into the PATH . The location of the Scripts\ folder is also added. This allows you to type python to run the interpreter, and pip for the package installer. Thus, you can also execute your scripts with command line options, see Command line documentation.
If you don’t enable this option at install time, you can always re-run the installer, select Modify, and enable it. Alternatively, you can manually modify the PATH using the directions in Excursus: Setting environment variables . You need to set your PATH environment variable to include the directory of your Python installation, delimited by a semicolon from other entries. An example variable could look like this (assuming the first two entries already existed):
3.4. Python Launcher for Windows¶
New in version 3.3.
The Python launcher for Windows is a utility which aids in locating and executing of different Python versions. It allows scripts (or the command-line) to indicate a preference for a specific Python version, and will locate and execute that version.
Unlike the PATH variable, the launcher will correctly select the most appropriate version of Python. It will prefer per-user installations over system-wide ones, and orders by language version rather than using the most recently installed version.
3.4.1. Getting started¶
3.4.1.1. From the command-line¶
Changed in version 3.6.
System-wide installations of Python 3.3 and later will put the launcher on your PATH . The launcher is compatible with all available versions of Python, so it does not matter which version is installed. To check that the launcher is available, execute the following command in Command Prompt:
You should find that the latest version of Python you have installed is started — it can be exited as normal, and any additional command-line arguments specified will be sent directly to Python.
If you have multiple versions of Python installed (e.g., 2.7 and 3.7) you will have noticed that Python 3.7 was started — to launch Python 2.7, try the command:
If you want the latest version of Python 2.x you have installed, try the command:
You should find the latest version of Python 2.x starts.
If you see the following error, you do not have the launcher installed:
Per-user installations of Python do not add the launcher to PATH unless the option was selected on installation.
3.4.1.2. Virtual environments¶
New in version 3.5.
If the launcher is run with no explicit Python version specification, and a virtual environment (created with the standard library venv module or the external virtualenv tool) active, the launcher will run the virtual environment’s interpreter rather than the global one. To run the global interpreter, either deactivate the virtual environment, or explicitly specify the global Python version.
3.4.1.3. From a script¶
Let’s create a test Python script — create a file called hello.py with the following contents
From the directory in which hello.py lives, execute the command:
You should notice the version number of your latest Python 2.x installation is printed. Now try changing the first line to be:
Re-executing the command should now print the latest Python 3.x information. As with the above command-line examples, you can specify a more explicit version qualifier. Assuming you have Python 2.6 installed, try changing the first line to #! python2.6 and you should find the 2.6 version information printed.
Note that unlike interactive use, a bare “python” will use the latest version of Python 2.x that you have installed. This is for backward compatibility and for compatibility with Unix, where the command python typically refers to Python 2.
3.4.1.4. From file associations¶
The launcher should have been associated with Python files (i.e. .py , .pyw , .pyc files) when it was installed. This means that when you double-click on one of these files from Windows explorer the launcher will be used, and therefore you can use the same facilities described above to have the script specify the version which should be used.
The key benefit of this is that a single launcher can support multiple Python versions at the same time depending on the contents of the first line.
3.4.2. Shebang Lines¶
If the first line of a script file starts with #! , it is known as a “shebang” line. Linux and other Unix like operating systems have native support for such lines and they are commonly used on such systems to indicate how a script should be executed. This launcher allows the same facilities to be used with Python scripts on Windows and the examples above demonstrate their use.
To allow shebang lines in Python scripts to be portable between Unix and Windows, this launcher supports a number of ‘virtual’ commands to specify which interpreter to use. The supported virtual commands are:
- /usr/bin/env python
- /usr/bin/python
- /usr/local/bin/python
- python
For example, if the first line of your script starts with
The default Python will be located and used. As many Python scripts written to work on Unix will already have this line, you should find these scripts can be used by the launcher without modification. If you are writing a new script on Windows which you hope will be useful on Unix, you should use one of the shebang lines starting with /usr .
Any of the above virtual commands can be suffixed with an explicit version (either just the major version, or the major and minor version) — for example /usr/bin/python2.7 — which will cause that specific version to be located and used.
The /usr/bin/env form of shebang line has one further special property. Before looking for installed Python interpreters, this form will search the executable PATH for a Python executable. This corresponds to the behaviour of the Unix env program, which performs a PATH search.
3.4.3. Arguments in shebang lines¶
The shebang lines can also specify additional options to be passed to the Python interpreter. For example, if you have a shebang line:
Then Python will be started with the -v option
3.4.4. Customization¶
3.4.4.1. Customization via INI files¶
Two .ini files will be searched by the launcher — py.ini in the current user’s “application data” directory (i.e. the directory returned by calling the Windows function SHGetFolderPath with CSIDL_LOCAL_APPDATA) and py.ini in the same directory as the launcher. The same .ini files are used for both the ‘console’ version of the launcher (i.e. py.exe) and for the ‘windows’ version (i.e. pyw.exe)
Customization specified in the “application directory” will have precedence over the one next to the executable, so a user, who may not have write access to the .ini file next to the launcher, can override commands in that global .ini file)
3.4.4.2. Customizing default Python versions¶
In some cases, a version qualifier can be included in a command to dictate which version of Python will be used by the command. A version qualifier starts with a major version number and can optionally be followed by a period (‘.’) and a minor version specifier. If the minor qualifier is specified, it may optionally be followed by “-32” to indicate the 32-bit implementation of that version be used.
For example, a shebang line of #!python has no version qualifier, while #!python3 has a version qualifier which specifies only a major version.
If no version qualifiers are found in a command, the environment variable PY_PYTHON can be set to specify the default version qualifier — the default value is “2”. Note this value could specify just a major version (e.g. “2”) or a major.minor qualifier (e.g. “2.6”), or even major.minor-32.
If no minor version qualifiers are found, the environment variable PY_PYTHON
On 64-bit Windows with both 32-bit and 64-bit implementations of the same (major.minor) Python version installed, the 64-bit version will always be preferred. This will be true for both 32-bit and 64-bit implementations of the launcher — a 32-bit launcher will prefer to execute a 64-bit Python installation of the specified version if available. This is so the behavior of the launcher can be predicted knowing only what versions are installed on the PC and without regard to the order in which they were installed (i.e., without knowing whether a 32 or 64-bit version of Python and corresponding launcher was installed last). As noted above, an optional “-32” suffix can be used on a version specifier to change this behaviour.
- If no relevant options are set, the commands python and python2 will use the latest Python 2.x version installed and the command python3 will use the latest Python 3.x installed.
- The commands python3.1 and python2.7 will not consult any options at all as the versions are fully specified.
- If PY_PYTHON=3 , the commands python and python3 will both use the latest installed Python 3 version.
- If PY_PYTHON=3.1-32 , the command python will use the 32-bit implementation of 3.1 whereas the command python3 will use the latest installed Python (PY_PYTHON was not considered at all as a major version was specified.)
- If PY_PYTHON=3 and PY_PYTHON3=3.1 , the commands python and python3 will both use specifically 3.1
In addition to environment variables, the same settings can be configured in the .INI file used by the launcher. The section in the INI file is called [defaults] and the key name will be the same as the environment variables without the leading PY_ prefix (and note that the key names in the INI file are case insensitive.) The contents of an environment variable will override things specified in the INI file.
- Setting PY_PYTHON=3.1 is equivalent to the INI file containing:
- Setting PY_PYTHON=3 and PY_PYTHON3=3.1 is equivalent to the INI file containing:
3.4.5. Diagnostics¶
If an environment variable PYLAUNCH_DEBUG is set (to any value), the launcher will print diagnostic information to stderr (i.e. to the console). While this information manages to be simultaneously verbose and terse, it should allow you to see what versions of Python were located, why a particular version was chosen and the exact command-line used to execute the target Python.
3.5. Finding modules¶
Python usually stores its library (and thereby your site-packages folder) in the installation directory. So, if you had installed Python to C:\Python\ , the default library would reside in C:\Python\Lib\ and third-party modules should be stored in C:\Python\Lib\site-packages\ .
To completely override sys.path , create a ._pth file with the same name as the DLL ( python36._pth ) or the executable ( python._pth ) and specify one line for each path to add to sys.path . The file based on the DLL name overrides the one based on the executable, which allows paths to be restricted for any program loading the runtime if desired.
When the file exists, all registry and environment variables are ignored, isolated mode is enabled, and site is not imported unless one line in the file specifies import site . Blank paths and lines starting with # are ignored. Each path may be absolute or relative to the location of the file. Import statements other than to site are not permitted, and arbitrary code cannot be specified.
Note that .pth files (without leading underscore) will be processed normally by the site module.
When no ._pth file is found, this is how sys.path is populated on Windows:
- An empty entry is added at the start, which corresponds to the current directory.
- If the environment variable PYTHONPATH exists, as described in Environment variables , its entries are added next. Note that on Windows, paths in this variable must be separated by semicolons, to distinguish them from the colon used in drive identifiers ( C:\ etc.).
- Additional “application paths” can be added in the registry as subkeys of \SOFTWARE\Python\PythonCore\ version \PythonPath under both the HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE hives. Subkeys which have semicolon-delimited path strings as their default value will cause each path to be added to sys.path . (Note that all known installers only use HKLM, so HKCU is typically empty.)
- If the environment variable PYTHONHOME is set, it is assumed as “Python Home”. Otherwise, the path of the main Python executable is used to locate a “landmark file” (either Lib\os.py or pythonXY.zip ) to deduce the “Python Home”. If a Python home is found, the relevant sub-directories added to sys.path ( Lib , plat-win , etc) are based on that folder. Otherwise, the core Python path is constructed from the PythonPath stored in the registry.
- If the Python Home cannot be located, no PYTHONPATH is specified in the environment, and no registry entries can be found, a default path with relative entries is used (e.g. .\Lib;.\plat-win , etc).
If a pyvenv.cfg file is found alongside the main executable or in the directory one level above the executable, the following variations apply:
- If home is an absolute path and PYTHONHOME is not set, this path is used instead of the path to the main executable when deducing the home location.
The end result of all this is:
- When running python.exe , or any other .exe in the main Python directory (either an installed version, or directly from the PCbuild directory), the core path is deduced, and the core paths in the registry are ignored. Other “application paths” in the registry are always read.
- When Python is hosted in another .exe (different directory, embedded via COM, etc), the “Python Home” will not be deduced, so the core path from the registry is used. Other “application paths” in the registry are always read.
- If Python can’t find its home and there are no registry value (frozen .exe, some very strange installation setup) you get a path with some default, but relative, paths.
For those who want to bundle Python into their application or distribution, the following advice will prevent conflicts with other installations:
- Include a ._pth file alongside your executable containing the directories to include. This will ignore paths listed in the registry and environment variables, and also ignore site unless import site is listed.
- If you are loading python3.dll or python36.dll in your own executable, explicitly call Py_SetPath() or (at least) Py_SetProgramName() before Py_Initialize() .
- Clear and/or overwrite PYTHONPATH and set PYTHONHOME before launching python.exe from your application.
- If you cannot use the previous suggestions (for example, you are a distribution that allows people to run python.exe directly), ensure that the landmark file ( Lib\os.py ) exists in your install directory. (Note that it will not be detected inside a ZIP file, but a correctly named ZIP file will be detected instead.)
These will ensure that the files in a system-wide installation will not take precedence over the copy of the standard library bundled with your application. Otherwise, your users may experience problems using your application. Note that the first suggestion is the best, as the other may still be susceptible to non-standard paths in the registry and user site-packages.
- Adds ._pth file support and removes applocal option from pyvenv.cfg .
- Adds pythonXX.zip as a potential landmark when directly adjacent to the executable.
Deprecated since version 3.6:
Modules specified in the registry under Modules (not PythonPath ) may be imported by importlib.machinery.WindowsRegistryFinder . This finder is enabled on Windows in 3.6.0 and earlier, but may need to be explicitly added to sys.meta_path in the future.
3.6. Additional modules¶
Even though Python aims to be portable among all platforms, there are features that are unique to Windows. A couple of modules, both in the standard library and external, and snippets exist to use these features.
The Windows-specific standard modules are documented in MS Windows Specific Services .
3.6.1. PyWin32¶
The PyWin32 module by Mark Hammond is a collection of modules for advanced Windows-specific support. This includes utilities for:
-
(COM)
- Win32 API calls
- Registry
- Event log (MFC) user interfaces
PythonWin is a sample MFC application shipped with PyWin32. It is an embeddable IDE with a built-in debugger.
Win32 How Do I. by Tim Golden Python and COM by David and Paul Boddie
3.6.2. cx_Freeze¶
cx_Freeze is a distutils extension (see Extending Distutils ) which wraps Python scripts into executable Windows programs ( * .exe files). When you have done this, you can distribute your application without requiring your users to install Python.
3.6.3. WConio¶
Since Python’s advanced terminal handling layer, curses , is restricted to Unix-like systems, there is a library exclusive to Windows as well: Windows Console I/O for Python.
WConio is a wrapper for Turbo-C’s CONIO.H , used to create text user interfaces.
3.7. Compiling Python on Windows¶
If you want to compile CPython yourself, first thing you should do is get the source. You can download either the latest release’s source or just grab a fresh checkout.
The source tree contains a build solution and project files for Microsoft Visual Studio 2015, which is the compiler used to build the official Python releases. These files are in the PCbuild directory.
Check PCbuild/readme.txt for general information on the build process.
Python + Windows + distutils + SWIG + gcc MinGW or “Creating Python extensions in C/C++ with SWIG and compiling them with MinGW gcc under Windows” or “Installing Python extension with distutils and without Microsoft Visual C++” by Sébastien Sauvage, 2003 MingW – Python extensions by Trent Apted et al, 2007
3.8. Embedded Distribution¶
New in version 3.5.
The embedded distribution is a ZIP file containing a minimal Python environment. It is intended for acting as part of another application, rather than being directly accessed by end-users.
When extracted, the embedded distribution is (almost) fully isolated from the user’s system, including environment variables, system registry settings, and installed packages. The standard library is included as pre-compiled and optimized .pyc files in a ZIP, and python3.dll , python36.dll , python.exe and pythonw.exe are all provided. Tcl/tk (including all dependants, such as Idle), pip and the Python documentation are not included.
The embedded distribution does not include the Microsoft C Runtime and it is the responsibility of the application installer to provide this. The runtime may have already been installed on a user’s system previously or automatically via Windows Update, and can be detected by finding ucrtbase.dll in the system directory.
Third-party packages should be installed by the application installer alongside the embedded distribution. Using pip to manage dependencies as for a regular Python installation is not supported with this distribution, though with some care it may be possible to include and use pip for automatic updates. In general, third-party packages should be treated as part of the application (“vendoring”) so that the developer can ensure compatibility with newer versions before providing updates to users.
The two recommended use cases for this distribution are described below.
3.8.1. Python Application¶
An application written in Python does not necessarily require users to be aware of that fact. The embedded distribution may be used in this case to include a private version of Python in an install package. Depending on how transparent it should be (or conversely, how professional it should appear), there are two options.
Using a specialized executable as a launcher requires some coding, but provides the most transparent experience for users. With a customized launcher, there are no obvious indications that the program is running on Python: icons can be customized, company and version information can be specified, and file associations behave properly. In most cases, a custom launcher should simply be able to call Py_Main with a hard-coded command line.
The simpler approach is to provide a batch file or generated shortcut that directly calls the python.exe or pythonw.exe with the required command-line arguments. In this case, the application will appear to be Python and not its actual name, and users may have trouble distinguishing it from other running Python processes or file associations.
With the latter approach, packages should be installed as directories alongside the Python executable to ensure they are available on the path. With the specialized launcher, packages can be located in other locations as there is an opportunity to specify the search path before launching the application.
3.8.2. Embedding Python¶
Applications written in native code often require some form of scripting language, and the embedded Python distribution can be used for this purpose. In general, the majority of the application is in native code, and some part will either invoke python.exe or directly use python3.dll . For either case, extracting the embedded distribution to a subdirectory of the application installation is sufficient to provide a loadable Python interpreter.
As with the application use, packages can be installed to any location as there is an opportunity to specify search paths before initializing the interpreter. Otherwise, there is no fundamental differences between using the embedded distribution and a regular installation.
3.9. Other resources¶
Python Programming On Win32 “Help for Windows Programmers” by Mark Hammond and Andy Robinson, O’Reilly Media, 2000, ISBN 1-56592-621-8 A Python for Windows Tutorial by Amanda Birmingham, 2004 PEP 397 — Python launcher for Windows The proposal for the launcher to be included in the Python distribution.