Select feature one by one not working in pyQGIS?

Question

I have used following code for selecting the features one by one. but when i run the script it is just selecting last feature and zoom it. I want to select each feature and zoom it.

def SelectFeatures(self):
    layer = self.iface.activeLayer();
    iter = layer.getFeatures();
    for feature in iter:
        geom = feature.geometry()
        self.iface.mapCanvas().setSelectionColor(QColor("yellow"));
        layer.setSelectedFeatures([feature.id()])
        selected_features = layer.selectedFeatures()
        self.iface.mapCanvas().zoomToSelected( layer )
        self.iface.mapCanvas().refresh()

Answer 1

You have to add these features to one list and then select all of them:

def SelectFeatures(self):
    layer = self.iface.activeLayer();
    iter = layer.getFeatures();
    selection = []
    for feature in iter:
        selection.append(feature.id())
    layer.setSelectedFeatures(selection)
    self.iface.mapCanvas().setSelectionColor(QColor("yellow"));
    selected_features = layer.selectedFeatures()
    self.iface.mapCanvas().zoomToSelected( layer )
    self.iface.mapCanvas().refresh()

Answer 2

I had a similar problem: QGIS waits with repainting until the commands started in the same thread finished. An adoption of this very good recipe How do I prevent Qgis from being detected as "not responding" when running a heavy plugin? did the job. Maybe the following works for you. I included a sleep() to slow down the process.

import time
from PyQt4 import QtCore

class Worker(QtCore.QObject):
    def __init__(self, layer, *args, **kwargs):
        QtCore.QObject.__init__(self, *args, **kwargs)
        self.layer = layer
        self.abort = False

    def run(self):
        try:
            self.feature_count = self.layer.featureCount()
            features = self.layer.getFeatures()
            for feature in features:
                if self.abort is True:
                    self.killed.emit()
                    break
                self.layer.setSelectedFeatures([feature.id()])
                selected_features = self.layer.selectedFeatures()
                self.repaint.emit(feature.id())
                time.sleep(0.5)
        except:
            self.finished.emit(False)
        else:
            self.finished.emit(True)

    def kill(self):
        self.abort = True

    killed = QtCore.pyqtSignal()
    finished = QtCore.pyqtSignal(bool)
    repaint = QtCore.pyqtSignal(int)

def repaint(id):
    global layer
    iface.mapCanvas().zoomToSelected(layer)
    try:
        path = 'E:\Test' + str(id) +'.png'
        iface.mapCanvas().saveAsImage(path)
    except:
        print 'ERROR: Writing to file %s failed' % path 
    # more instructions ...
    iface.mapCanvas().refresh()

# get active layer
layer = iface.activeLayer()
iface.mapCanvas().setSelectionColor(QColor("yellow"));

thread = QtCore.QThread()
worker = Worker(layer)
worker.moveToThread(thread)
thread.started.connect(worker.run)
worker.finished.connect(worker.deleteLater)
thread.finished.connect(thread.deleteLater)
worker.finished.connect(thread.quit)
worker.repaint.connect(repaint)
thread.start()