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Algorithms and other processing code should use this method (instead of dataobjects.getLayerFromString) to retrieve layers from a string, as it considers the processing context and allows resolving strings to temporarily stored layers. This permits processing models to function correctly when intermediate results are stored as memory layers. Subsequent model algorithms can then access these temporary layers as inputs. All temporary layers will be removed when the context object is destroyed after the model algorithm is run.
101 lines
3.7 KiB
Python
101 lines
3.7 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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DeleteColumn.py
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---------------------
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Date : May 2010
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Copyright : (C) 2010 by Michael Minn
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Email : pyqgis at michaelminn dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Michael Minn'
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__date__ = 'May 2010'
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__copyright__ = '(C) 2010, Michael Minn'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsApplication,
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QgsProcessingUtils)
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.parameters import ParameterVector
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from processing.core.parameters import ParameterTableField
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from processing.core.outputs import OutputVector
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from processing.tools import dataobjects, vector
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class DeleteColumn(GeoAlgorithm):
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INPUT = 'INPUT'
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COLUMNS = 'COLUMN'
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OUTPUT = 'OUTPUT'
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def icon(self):
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return QgsApplication.getThemeIcon("/providerQgis.svg")
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def svgIconPath(self):
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return QgsApplication.iconPath("providerQgis.svg")
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def tags(self):
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return self.tr('drop,delete,remove,fields,columns,attributes').split(',')
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def group(self):
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return self.tr('Vector table tools')
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def name(self):
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return 'deletecolumn'
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def displayName(self):
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return self.tr('Delete column')
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def defineCharacteristics(self):
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self.addParameter(ParameterVector(self.INPUT,
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self.tr('Input layer')))
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self.addParameter(ParameterTableField(self.COLUMNS,
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self.tr('Fields to delete'), self.INPUT, multiple=True))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Output layer')))
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def processAlgorithm(self, context, feedback):
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layer = dataobjects.QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
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fields_to_delete = self.getParameterValue(self.COLUMNS).split(';')
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fields = layer.fields()
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field_indices = []
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# loop through twice - first we need to build up a list of original attribute indices
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for f in fields_to_delete:
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index = fields.lookupField(f)
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field_indices.append(index)
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# important - make sure we remove from the end so we aren't changing used indices as we go
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field_indices.sort(reverse=True)
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# this second time we make a cleaned version of the fields
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for index in field_indices:
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fields.remove(index)
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writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields, layer.wkbType(), layer.crs(), context)
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features = QgsProcessingUtils.getFeatures(layer, context)
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total = 100.0 / QgsProcessingUtils.featureCount(layer, context)
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for current, f in enumerate(features):
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attributes = f.attributes()
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for index in field_indices:
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del attributes[index]
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f.setAttributes(attributes)
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writer.addFeature(f)
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feedback.setProgress(int(current * total))
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del writer
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