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Pylance
Fast, feature-rich language support for Python
This repository is for providing feedback and documentation on the Pylance language server extension in Visual Studio Code. You can use the repository to report issues or submit feature requests. The Pylance codebase is not open-source but you can contribute to Pyright to make improvements to the core typing engine that powers the Pylance experience.
Pylance is the default language support for Python in Visual Studio Code and is shipped as part of that extension as an optional dependency.
The Pylance name is a small ode to Monty Python's Lancelot who was the first knight to answer the bridgekeeper's questions in the Holy Grail.
Quick Start
Install the Python extension from the marketplace. Pylance will be installed as an optional extension.
Open a Python (.py) file and the Pylance extension will activate.
Note: If you've previously set a language server and want to try Pylance, make sure you've set "python.languageServer": "Default" or "Pylance" in your settings.json file using the text editor, or using the Settings Editor UI.
Features
Pylance provides some awesome features for Python 3, including:
Docstrings
Signature help, with type information
Parameter suggestions
Code completion
Auto-imports (as well as add and remove import code actions)
As-you-type reporting of code errors and warnings (diagnostics)
Code outline
Code navigation
Type checking mode
Native multi-root workspace support
Jupyter Notebooks compatibility
Semantic highlighting
Generate Dependency File command for workspace roots, Explorer folders, and Python scripts (Pylance: Generate Dependency File)
Toggle Block Comment command for Python (Pylance: Toggle Block Comment)
Install Matching Type Stubs command that finds and installs type stub packages for your installed dependencies (Pylance: Install Matching Type Stubs)
Copilot Chat skills for fact-grounded Python help, type inference, inline type annotations, finding reviewed third-party stubs, stub authoring, Pylance docs, refactoring, profiling, improving Pylance type-evaluation performance, and adding or dropping Python version support
See the changelog for the latest release.
Settings and Customization
Pylance provides users with the ability to customize their Python language support via a host of settings which can either be placed in the settings.json file in your workspace, or edited through the Settings Editor UI.
python.analysis.languageServerMode
Offers predefined configurations to help users optimize Pylance's performance based on their development needs. It controls how many IntelliSense features Pylance provides, allowing you to choose between full language service functionality or a lightweight experience optimized for performance.
Default value: default
Available values:
light
default (default)
full
Description:
default: Provides a balanced experience with many useful features enabled by default. It ensures that the language server delivers sufficient functionality for most users without overloading the system. Advanced features can be enabled as needed, allowing for further customization at the cost of performance.
light: Designed for users seeking a lightweight, memory-efficient setup. This mode disables various features to make Pylance function more like a streamlined text editor. Ideal for those who do not require the full breadth of IntelliSense capabilities and prefer Pylance to be as resource-friendly as possible.
full: Designed for users seeking the most extensive feature set. This mode enables most of Pylance's features, offering the richest IntelliSense experience. Ideal for those who want access to the full range of available functionality.
Individual settings can be configured to override the defaults set by languageServerMode.
Default settings based on mode are:
Mode
light
default
full
python.analysis.exclude
["**"]
[]
[]
python.analysis.useLibraryCodeForTypes
false
true
true
python.analysis.enablePytestSupport
false
true
true
python.analysis.indexing
false
true
true
python.analysis.userFileIndexFollowSymlinkedFolders
true
true
true
python.analysis.autoImportCompletions
false
false
true
python.analysis.showOnlyDirectDependenciesInAutoImport
false
false
true
python.analysis.packageIndexDepths
See
settings
below
python.analysis.regenerateStdLibIndices
false
false
true
python.analysis.userFileIndexingLimit
2000
2000
-1
python.analysis.includeAliasesFromUserFiles
false
false
true
python.analysis.inlayHints.functionReturnTypes
false
false
true
python.analysis.inlayHints.pytestParameters
false
false
true
python.analysis.supportRestructuredText
true
true
true
python.analysis.supportDocstringTemplate
false
false
false
python.analysis.nodeExecutable
""
""
"auto"
python.analysis.typeCheckingMode
Used to specify the level of type checking analysis performed.
Default: off.
Note that the value of this setting can be overridden by having a pyrightconfig.json or a pyproject.toml. For more information see this link.
Available values:
off: Most type-checking diagnostics are disabled; unresolved imports/variables diagnostics are produced.
basic: All rules from off + basic type checking rules.
standard: All rules from basic + standard type checking rules.
strict: All rules from standard + strict type checking rules.
You can refer to pyright documentation to reference the default type checking rules for each of the type checking modes.
Performance Consideration:
Setting python.analysis.typeCheckingMode to off can improve performance by reducing diagnostic checks, especially in large codebases.
python.analysis.diagnosticMode
Used to allow a user to specify which files receive full diagnostics.
Available values:
workspace
openFilesOnly (default)
Performance Consideration:
Setting python.analysis.diagnosticMode to openFilesOnly limits full diagnostics to open files, reducing checking in large workspaces. Imported dependencies ca
Read the full README on GitHub