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Since it's safe to evaluate parameters in background threads now, it's usually going to be ok to evaluate everything in the processAlgorithm step. This keeps the algorithm code as simple as possible, and will make porting faster. Note that the prepare/postProcess virtual methods still exist and can be used when an algorithm MUST do setup/cleanup work in the main thread.
104 lines
3.9 KiB
Python
104 lines
3.9 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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QgsFeatureSink,
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QgsProcessingUtils,
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QgsProcessingParameterFeatureSource,
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QgsProcessingParameterFeatureSink,
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QgsProcessingParameterField,
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QgsProcessingOutputVectorLayer)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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class DeleteColumn(QgisAlgorithm):
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INPUT = 'INPUT'
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COLUMNS = 'COLUMN'
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OUTPUT = 'OUTPUT'
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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 __init__(self):
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super().__init__()
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self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT, self.tr('Input layer')))
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self.addParameter(QgsProcessingParameterField(self.COLUMNS,
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self.tr('Fields to drop'),
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None, self.INPUT, QgsProcessingParameterField.Any, True))
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self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Output layer')))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr("Output layer")))
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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('Drop field(s)')
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def processAlgorithm(self, parameters, context, feedback):
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source = self.parameterAsSource(parameters, self.INPUT, context)
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fields_to_delete = self.parameterAsFields(parameters, self.COLUMNS, context)
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fields = source.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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(sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
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fields, source.wkbType(), source.sourceCrs())
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features = source.getFeatures()
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total = 100.0 / source.featureCount() if source.featureCount() else 0
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for current, f in enumerate(features):
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if feedback.isCanceled():
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break
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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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sink.addFeature(f, QgsFeatureSink.FastInsert)
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feedback.setProgress(int(current * total))
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return {self.OUTPUT: dest_id}
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