Source code for safe_qgis.impact_calculator_thread

"""
InaSAFE Disaster risk assessment tool developed by AusAid -
**ISImpactCalculatorThread.**

The module provides a high level interface for running SAFE scenarios.

Contact : ole.moller.nielsen@gmail.com

.. note:: This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.

"""

__author__ = 'tim@linfiniti.com, ole.moller.nielsen@gmail.com'
__date__ = '11/01/2011'
__copyright__ = ('Copyright 2012, Australia Indonesia Facility for '
                 'Disaster Reduction')

import threading
import traceback
import sys

from PyQt4.QtCore import (QObject,
                          pyqtSignal)

from safe_qgis.safe_interface import calculateSafeImpact
from safe_qgis.exceptions import InsufficientParametersException


[docs]class ImpactCalculatorThread(threading.Thread, QObject): """A threaded class to compute an impact scenario. Under python a thread can only be run once, so the instances based on this class are designed to be short lived. We inherit from QObject so that we can use Qt translation self.tr calls and emit signals. .. todo:: implement this class using QThread as a base class since it supports thread termination which python threading doesnt seem to do. Also see the techbase article below for emitting signals across threads using Qt.QueuedConnection. http://techbase.kde.org/Development/Tutorials/ Python_introduction_to_signals_and_slots Users of this of this class can listen for signals indicating when processing is done. For example:: from is_impact_calculator_thread import ImpactCalculatorThread n = ImpactCalculatorThread() n.done.connect(n.showMessage) n.done.emit() Prints 'hello' to the console .. seealso:: http://techbase.kde.org/Development/Tutorials/ Python_introduction_to_signals_and_slots for an alternative (maybe nicer?) approach. """ done = pyqtSignal()
[docs] def showMessage(self): """For testing only""" print 'hello'
def __init__(self, theHazardLayer, theExposureLayer, theFunction): """Constructor for the impact calculator thread. Args: * Hazard layer: InaSAFE read_layer object containing the Hazard data. * Exposure layer: InaSAFE read_layer object containing the Exposure data. * Function: a InaSAFE function that defines how the Hazard assessment will be computed. Returns: None Raises: InsufficientParametersException if not all parameters are set. Requires three parameters to be set before execution can take place: """ threading.Thread.__init__(self) QObject.__init__(self) self._hazardLayer = theHazardLayer self._exposureLayer = theExposureLayer self._function = theFunction self._impactLayer = None self._result = None self._exception = None self._traceback = None
[docs] def impactLayer(self): """Return the InaSAFE layer instance which is the output from the last run.""" return self._impactLayer
[docs] def result(self): """Return the result of the last run.""" return self._result
[docs] def lastException(self): """Return any exception that may have been raised while running""" return self._exception
[docs] def lastTraceback(self): """Return the strack trace for any exception that may of occurred while running.""" return self._traceback
[docs] def run(self): """ Main function for hazard impact calculation thread. Requires three properties to be set before execution can take place: * Hazard layer - a path to a raster, * Exposure layer - a path to a vector points layer. * Function - a function that defines how the Hazard assessment will be computed. After the thread is complete, you can use the filename and result accessors to determine what the result of the analysis was:: calculator = ImpactCalculator() rasterPath = os.path.join(TESTDATA, 'xxx.asc') vectorPath = os.path.join(TESTDATA, 'xxx.shp') calculator.setHazardLayer(self.rasterPath) calculator.setExposureLayer(self.vectorPath) calculator.setFunction('Flood Building Impact Function') myRunner = calculator.getRunner() #wait till completion myRunner.join() myResult = myRunner.result() myFilename = myRunner.filename() Args: None. Returns: None Raises: InsufficientParametersException set. """ if (self._hazardLayer is None or self._exposureLayer is None or self._function is None): myMessage = self.tr('Ensure that hazard, exposure and function ' 'are all set before trying to run the ' 'analysis.') raise InsufficientParametersException(myMessage) try: myLayers = [self._hazardLayer, self._exposureLayer] self._impactLayer = calculateSafeImpact(theLayers=myLayers, theFunction=self._function) # Catch and handle all exceptions: # pylint: disable=W0703 except Exception, e: myMessage = self.tr('Calculation error encountered:\n') #store the exception so that controller class can get it later self._exception = e self._traceback = traceback.format_tb(sys.exc_info()[2]) print myMessage self._result = myMessage else: self._result = self.tr('Calculation completed successfully.') # pylint: enable=W0703 # Let any listening slots know we are done self.done.emit()