Class: QgsApplication

class qgis.core.QgsApplication

Bases: PyQt5.QtWidgets.QApplication

Extends QApplication to provide access to QGIS specific resources such as theme paths, database paths etc.

This is a subclass of QApplication and should be instantiated in place of QApplication. Most methods are static in keeping with the design of QApplication.

This class hides platform-specific path information and provides a portable way of referencing specific files and directories. Ideally, hard-coded paths should appear only here and not in other modules so that platform-conditional code is minimized and paths are easier to change due to centralization.

Enums

Methods

absolutePathToRelativePath

Converts absolute path to path relative to target

actionScopeRegistry

Returns the action scope registry.

activeThemePath

Returns the path to the currently active theme directory.

appIconPath

Gets application icon

applyGdalSkippedDrivers

Apply the skipped drivers list to gdal

authManager

Returns the application’s authentication manager instance

authorsFilePath

Returns the path to the authors file.

buildOutputPath

Returns path to the build output directory.

buildSourcePath

Returns path to the source directory.

childEvent

collectTranslatableObjects

Emits the signal to collect all the strings of .qgs to be included in ts file

colorSchemeRegistry

Returns the application’s color scheme registry, used for managing color schemes.

connectNotify

contributorsFilePath

Returns the path to the contributors file.

createDatabase

initialize qgis.db

createThemeFolder

Create the users theme folder

customEvent

customVariables

Custom expression variables for this application.

dataItemProviderRegistry

Returns the application’s data item provider registry, which keeps a list of data item providers that may add items to the browser tree.

defaultStylePath

Returns the path to default style (works as a starting point).

defaultThemePath

Returns the path to the default theme directory.

defaultThemesFolder

Returns the path to default themes folder from install (works as a starting point).

developersMapFilePath

Returns the path to the developers map file.

disconnectNotify

donorsFilePath

Returns the path to the donors file.

endian

Returns whether this machine uses big or little endian

event

Watch for QFileOpenEvent.

exitQgis

deletes provider registry and map layer registry

fieldFormatterRegistry

Gets the registry of available field formatters.

getThemeCursor

Helper to get a theme cursor.

getThemeIcon

Helper to get a theme icon.

getThemePixmap

Helper to get a theme icon as a pixmap.

gpsConnectionRegistry

Returns the application’s GPS connection registry, used for managing GPS connections.

i18nPath

Returns the path to the translation directory.

iconPath

Returns path to the desired icon file.

iconsPath

Returns the path to the icons image directory.

initQgis

loads providers

instance

Returns the singleton instance of the QgsApplication.

isRunningFromBuildDir

Indicates whether running from build directory (not installed)

isSignalConnected

layoutItemRegistry

Returns the application’s layout item registry, used for layout item types.

layoutTemplatePaths

Returns the paths to layout template directories.

libexecPath

Returns the path with utility executables (help viewer, crssync, …)

libraryPath

Returns the path containing qgis_core, qgis_gui, qgispython (and other) libraries

licenceFilePath

Returns the path to the licence file.

locale

Returns the QGIS locale.

maxConcurrentConnectionsPerPool

The maximum number of concurrent connections per connections pool.

maxThreads

Gets maximum concurrent thread count

messageLog

Returns the application’s message log.

metadataPath

Returns the path to the metadata directory.

networkContentFetcherRegistry

Returns the application’s network content registry used for fetching temporary files during QGIS session

notify

Catch exceptions when sending event to receiver.

nullRepresentation

This string is used to represent the value NULL throughout QGIS.

osName

Returns a string name of the operating system QGIS is running on.

pageSizeRegistry

Returns the application’s page size registry, used for managing layout page sizes.

paintEffectRegistry

Returns the application’s paint effect registry, used for managing paint effects.

pkgDataPath

Returns the common root path of all application data directories.

platform

Returns the QGIS platform name, e.g., “desktop” or “server”.

pluginLayerRegistry

Returns the application’s plugin layer registry, used for managing plugin layer types.

pluginPath

Returns the path to the application plugin directory.

prefixPath

Returns the path to the application prefix directory.

processingRegistry

Returns the application’s processing registry, used for managing processing providers, algorithms, and various parameters and outputs.

profiler

Returns the application runtime profiler.

projectStorageRegistry

Returns registry of available project storage implementations.

qgisAuthDatabaseFilePath

Returns the path to the user authentication database file: qgis-auth.db.

qgisMasterDatabaseFilePath

Returns the path to the master qgis.db file.

qgisSettingsDirPath

Returns the path to the settings directory in user’s home dir

qgisUserDatabaseFilePath

Returns the path to the user qgis.db file.

qmlImportPath

Returns the path where QML components are installed for QGIS Quick library.

receivers

registerOgrDrivers

Register OGR drivers ensuring this only happens once.

relativePathToAbsolutePath

Converts path relative to target to an absolute path

renderer3DRegistry

Returns registry of available 3D renderers.

rendererRegistry

Returns the application’s renderer registry, used for managing vector layer renderers.

reportStyleSheet

Returns a standard css style sheet for reports.

resolvePkgPath

Calculate the application pkg path

restoreGdalDriver

Sets the GDAL_SKIP environment variable to exclude the specified driver and then calls GDALDriverManager.AutoSkipDrivers() to unregister it.

sender

senderSignalIndex

serverResourcesPath

Returns the path to the server resources directory.

setAuthDatabaseDirPath

Alters authentication data base directory path - used by 3rd party apps

setCustomVariable

Set a single custom expression variable.

setCustomVariables

Custom expression variables for this application.

setDefaultSvgPaths

Alters default svg paths - used by 3rd party apps.

setFileOpenEventReceiver

Sets the FileOpen event receiver

setMaxThreads

Set maximum concurrent thread count

setNullRepresentation

copydoc nullRepresentation()

setPkgDataPath

Alters pkg data path - used by 3rd party apps

setPluginPath

Alters plugin path - used by 3rd party apps

setPrefixPath

Alters prefix path - used by 3rd party apps

setThemeName

Set the active theme to the specified theme.

setTranslation

Set translation

setUITheme

Set the current UI theme used to style the interface.

shortNameRegExp

Returns the short name regular expression for line edit validator

showSettings

Convenience function to get a summary of the paths used in this application instance useful for debugging mainly.*

skipGdalDriver

Sets the GDAL_SKIP environment variable to include the specified driver and then calls GDALDriverManager.AutoSkipDrivers() to unregister it.

skippedGdalDrivers

Returns the list of gdal drivers that should be skipped (based on GDAL_SKIP environment variable)

splashPath

Returns the path to the splash screen image directory.

sponsorsFilePath

Returns the path to the sponsors file.

srsDatabaseFilePath

Returns the path to the srs.db file.

svgCache

Returns the application’s SVG cache, used for caching SVG images and handling parameter replacement within SVG files.

svgPaths

Returns the paths to svg directories.

symbolLayerRegistry

Returns the application’s symbol layer registry, used for managing symbol layers.

systemEnvVars

Returns the system environment variables passed to application.

taskManager

Returns the application’s task manager, used for managing application wide background task handling.

themeName

Set the active theme to the specified theme.

timerEvent

translatorsFilePath

Returns the path to the sponsors file.

uiThemes

All themes found in ~/.qgis3/themes folder.

userFullName

Returns the user’s operating system login account full display name.

userLoginName

Returns the user’s operating system login account name.

userStylePath

Returns the path to user’s style.

userThemesFolder

Returns the path to user’s themes folder

Signals

customVariablesChanged

Emitted whenever a custom global variable changes.

nullRepresentationChanged

copydoc nullRepresentation() [signal]

requestForTranslatableObjects

Emitted when project strings which require translation are being collected for inclusion in a .ts file.

Attributes

CapturePoint

CrossHair

Identify

NDR

QGIS_APPLICATION_NAME

QGIS_ORGANIZATION_DOMAIN

QGIS_ORGANIZATION_NAME

Sampler

Select

XDR

ZoomIn

ZoomOut

CapturePoint = 4
CrossHair = 3
class Cursor

Bases: int

Identify = 2
NDR = 1
QGIS_APPLICATION_NAME = 'QGIS3'
QGIS_ORGANIZATION_DOMAIN = 'qgis.org'
QGIS_ORGANIZATION_NAME = 'QGIS'
Sampler = 6
Select = 5
XDR = 0
ZoomIn = 0
ZoomOut = 1
absolutePathToRelativePath(apath: str, targetPath: str) → str

Converts absolute path to path relative to target

actionScopeRegistry() → QgsActionScopeRegistry

Returns the action scope registry.

New in version 3.0.

activeThemePath() → str

Returns the path to the currently active theme directory.

appIconPath() → str

Gets application icon

applyGdalSkippedDrivers()

Apply the skipped drivers list to gdal

See also

skipGdalDriver()

authManager() → QgsAuthManager

Returns the application’s authentication manager instance

Note

this can be a null pointer if called before initQgis

See also

initQgis()

New in version 3.0.

authorsFilePath() → str

Returns the path to the authors file.

buildOutputPath() → str

Returns path to the build output directory. Valid only when running from build directory

buildSourcePath() → str

Returns path to the source directory. Valid only when running from build directory

childEvent()
collectTranslatableObjects(self, translationContext: QgsTranslationContext)

Emits the signal to collect all the strings of .qgs to be included in ts file

New in version 3.4.

colorSchemeRegistry() → QgsColorSchemeRegistry

Returns the application’s color scheme registry, used for managing color schemes.

New in version 3.0.

connectNotify()
contributorsFilePath() → str

Returns the path to the contributors file. Contributors are people who have submitted patches but don’t have commit access. *

createDatabase(errorMessage: str = '') → bool

initialize qgis.db

createThemeFolder() → bool

Create the users theme folder

customEvent()
customVariables() → Dict[str, Any]

Custom expression variables for this application. This does not include generated variables (like system name, user name etc.)

New in version 3.0.

customVariablesChanged

Emitted whenever a custom global variable changes.

New in version 3.0: [signal]

dataItemProviderRegistry() → QgsDataItemProviderRegistry

Returns the application’s data item provider registry, which keeps a list of data item providers that may add items to the browser tree.

New in version 3.0.

defaultStylePath() → str

Returns the path to default style (works as a starting point).

defaultThemePath() → str

Returns the path to the default theme directory.

defaultThemesFolder() → str

Returns the path to default themes folder from install (works as a starting point).

developersMapFilePath() → str

Returns the path to the developers map file. The developers map was created by using leaflet framework, it shows the contributors.json file.

New in version 2.7.

disconnectNotify()
donorsFilePath() → str

Returns the path to the donors file.

endian() → QgsApplication.endian_t

Returns whether this machine uses big or little endian

class endian_t

Bases: int

event(self, event: QEvent) → bool

Watch for QFileOpenEvent.

exitQgis()

deletes provider registry and map layer registry

fieldFormatterRegistry() → QgsFieldFormatterRegistry

Gets the registry of available field formatters.

getThemeCursor(cursor: QgsApplication.Cursor) → QCursor

Helper to get a theme cursor. It will fall back to the default theme if the active theme does not have the required icon. Cursors are automatically scaled to look like a 16px cursor on 96dpi screens.

getThemeIcon(name: str) → QIcon

Helper to get a theme icon. It will fall back to the default theme if the active theme does not have the required icon.

getThemePixmap(name: str) → QPixmap

Helper to get a theme icon as a pixmap. It will fall back to the default theme if the active theme does not have the required icon.

gpsConnectionRegistry() → QgsGpsConnectionRegistry

Returns the application’s GPS connection registry, used for managing GPS connections.

New in version 3.0.

i18nPath() → str

Returns the path to the translation directory.

iconPath(iconFile: str) → str

Returns path to the desired icon file. First it tries to use the active theme path, then default theme path

iconsPath() → str

Returns the path to the icons image directory.

initQgis()

loads providers

instance() → QgsApplication

Returns the singleton instance of the QgsApplication.

New in version 3.0.

isRunningFromBuildDir() → bool

Indicates whether running from build directory (not installed)

isSignalConnected()
layoutItemRegistry() → QgsLayoutItemRegistry

Returns the application’s layout item registry, used for layout item types.

New in version 3.0.

layoutTemplatePaths() → List[str]

Returns the paths to layout template directories.

New in version 3.0.

libexecPath() → str

Returns the path with utility executables (help viewer, crssync, …)

libraryPath() → str

Returns the path containing qgis_core, qgis_gui, qgispython (and other) libraries

licenceFilePath() → str

Returns the path to the licence file.

locale() → str

Returns the QGIS locale.

New in version 3.0.

maxConcurrentConnectionsPerPool(self) → int

The maximum number of concurrent connections per connections pool.

Note

QGIS may in some situations allocate more than this amount of connections to avoid deadlocks.

New in version 3.4.

maxThreads() → int

Gets maximum concurrent thread count

New in version 2.4.

messageLog() → QgsMessageLog

Returns the application’s message log.

New in version 3.0.

metadataPath() → str

Returns the path to the metadata directory.

New in version 3.0.

networkContentFetcherRegistry() → QgsNetworkContentFetcherRegistry

Returns the application’s network content registry used for fetching temporary files during QGIS session

New in version 3.2.

notify(self, receiver: QObject, event: QEvent) → bool

Catch exceptions when sending event to receiver.

nullRepresentation() → str

This string is used to represent the value NULL throughout QGIS.

In general, when passing values around, prefer to use a null QVariant QVariant( field.type() ) or QVariant( QVariant.Int ). This value should only be used in the final presentation step when showing values in a widget or sending it to a web browser.

nullRepresentationChanged

copydoc nullRepresentation() [signal]

osName() → str

Returns a string name of the operating system QGIS is running on.

See also

platform()

New in version 2.14.

pageSizeRegistry() → QgsPageSizeRegistry

Returns the application’s page size registry, used for managing layout page sizes.

New in version 3.0.

paintEffectRegistry() → QgsPaintEffectRegistry

Returns the application’s paint effect registry, used for managing paint effects.

New in version 3.0.

pkgDataPath() → str

Returns the common root path of all application data directories.

platform() → str

Returns the QGIS platform name, e.g., “desktop” or “server”.

See also

osName()

New in version 2.14.

pluginLayerRegistry() → QgsPluginLayerRegistry

Returns the application’s plugin layer registry, used for managing plugin layer types.

New in version 3.0.

pluginPath() → str

Returns the path to the application plugin directory.

prefixPath() → str

Returns the path to the application prefix directory.

processingRegistry() → QgsProcessingRegistry

Returns the application’s processing registry, used for managing processing providers, algorithms, and various parameters and outputs.

New in version 3.0.

profiler() → QgsRuntimeProfiler

Returns the application runtime profiler.

New in version 3.0.

projectStorageRegistry() → QgsProjectStorageRegistry

Returns registry of available project storage implementations.

New in version 3.2.

qgisAuthDatabaseFilePath() → str

Returns the path to the user authentication database file: qgis-auth.db.

qgisMasterDatabaseFilePath() → str

Returns the path to the master qgis.db file.

qgisSettingsDirPath() → str

Returns the path to the settings directory in user’s home dir

qgisUserDatabaseFilePath() → str

Returns the path to the user qgis.db file.

qmlImportPath() → str

Returns the path where QML components are installed for QGIS Quick library. Returns empty string when QGIS is built without Quick support

New in version 3.2.

receivers()
registerOgrDrivers()

Register OGR drivers ensuring this only happens once. This is a workaround for an issue with older gdal versions that caused duplicate driver name entries to appear in the list of registered drivers when QgsApplication.registerOgrDrivers was called multiple times.

relativePathToAbsolutePath(rpath: str, targetPath: str) → str

Converts path relative to target to an absolute path

renderer3DRegistry() → Qgs3DRendererRegistry

Returns registry of available 3D renderers.

New in version 3.0.

rendererRegistry() → QgsRendererRegistry

Returns the application’s renderer registry, used for managing vector layer renderers.

New in version 3.0.

reportStyleSheet() → str

Returns a standard css style sheet for reports.

Typically you will use this method by doing: QString myStyle = QgsApplication.reportStyleSheet(); textBrowserReport->document()->setDefaultStyleSheet(myStyle);

Returns

QString containing the CSS 2.1 compliant stylesheet.

Note

you can use the special Qt extensions too, for example the gradient fills for backgrounds.

requestForTranslatableObjects

Emitted when project strings which require translation are being collected for inclusion in a .ts file. In order to register translatable strings, connect to this signal and register the strings within the specified translationContext.

New in version 3.4: [signal]

resolvePkgPath() → str

Calculate the application pkg path

Returns

the resolved pkg path

restoreGdalDriver(driver: str)

Sets the GDAL_SKIP environment variable to exclude the specified driver and then calls GDALDriverManager.AutoSkipDrivers() to unregister it. The driver name should be the short format of the Gdal driver name e.g. GTIFF.

sender()
senderSignalIndex()
serverResourcesPath() → str

Returns the path to the server resources directory.

setAuthDatabaseDirPath(authDbDirPath: str)

Alters authentication data base directory path - used by 3rd party apps

setCustomVariable(name: str, value: Any)

Set a single custom expression variable.

New in version 3.0.

setCustomVariables(customVariables: Dict[str, Any])

Custom expression variables for this application. Do not include generated variables (like system name, user name etc.)

New in version 3.0.

setDefaultSvgPaths(pathList: Iterable[str])

Alters default svg paths - used by 3rd party apps.

setFileOpenEventReceiver(receiver: QObject)

Sets the FileOpen event receiver

setMaxThreads(maxThreads: int)

Set maximum concurrent thread count

Note

must be between 1 and #cores, -1 means use all available cores

New in version 2.4.

setNullRepresentation(nullRepresentation: str)

copydoc nullRepresentation()

setPkgDataPath(pkgDataPath: str)

Alters pkg data path - used by 3rd party apps

setPluginPath(pluginPath: str)

Alters plugin path - used by 3rd party apps

setPrefixPath(prefixPath: str, useDefaultPaths: bool = False)

Alters prefix path - used by 3rd party apps

setThemeName(themeName: str)

Set the active theme to the specified theme. The theme name should be a single word e.g. ‘default’,’classic’. The theme search path usually will be pkgDataPath + “/themes/” + themName + “/” but plugin writers etc can use themeName() as a basis for searching for resources in their own datastores e.g. a Qt4 resource bundle.

Note

A basic test will be carried out to ensure the theme search path based on the supplied theme name exists. If it does not the theme name will be reverted to ‘default’.

setTranslation(translation: str)

Set translation

New in version 3.4.

setUITheme(themeName: str)

Set the current UI theme used to style the interface. Use uiThemes() to find valid themes to use. Variables found in variables.qss will be added to the stylesheet on load.

Parameters

themeName – The name of the theme.

Note

using an invalid theme name will reset to default

shortNameRegExp() → QRegExp

Returns the short name regular expression for line edit validator

showSettings() → str

Convenience function to get a summary of the paths used in this application instance useful for debugging mainly.*

skipGdalDriver(driver: str)

Sets the GDAL_SKIP environment variable to include the specified driver and then calls GDALDriverManager.AutoSkipDrivers() to unregister it. The driver name should be the short format of the Gdal driver name e.g. GTIFF.

skippedGdalDrivers() → List[str]

Returns the list of gdal drivers that should be skipped (based on GDAL_SKIP environment variable)

splashPath() → str

Returns the path to the splash screen image directory.

sponsorsFilePath() → str

Returns the path to the sponsors file.

srsDatabaseFilePath() → str

Returns the path to the srs.db file.

svgCache() → QgsSvgCache

Returns the application’s SVG cache, used for caching SVG images and handling parameter replacement within SVG files.

New in version 3.0.

svgPaths() → List[str]

Returns the paths to svg directories.

symbolLayerRegistry() → QgsSymbolLayerRegistry

Returns the application’s symbol layer registry, used for managing symbol layers.

New in version 3.0.

systemEnvVars() → Dict[str, str]

Returns the system environment variables passed to application.

taskManager() → QgsTaskManager

Returns the application’s task manager, used for managing application wide background task handling.

New in version 3.0.

themeName() → str

Set the active theme to the specified theme. The theme name should be a single word e.g. ‘default’,’classic’. The theme search path usually will be pkgDataPath + “/themes/” + themName + “/” but plugin writers etc can use this method as a basis for searching for resources in their own datastores e.g. a Qt4 resource bundle.

timerEvent()
translatorsFilePath() → str

Returns the path to the sponsors file.

uiThemes() → object

All themes found in ~/.qgis3/themes folder. The path is to the root folder for the theme

Returns

A hash of theme name and theme path. Valid theme folders contain style.qss

Note

Valid theme folders must contain a style.qss file.

userFullName() → str

Returns the user’s operating system login account full display name.

See also

userLoginName()

New in version 2.14.

userLoginName() → str

Returns the user’s operating system login account name.

See also

userFullName()

New in version 2.14.

userStylePath() → str

Returns the path to user’s style.

userThemesFolder() → str

Returns the path to user’s themes folder