pyqgis - Using QgsExpression.evaluate() on vector layer closes QGIS

I am trying to import a csv layer and run QgsExpression.evaluate() to make some computations on existing columns. However, QGIS 2.18, 3.2, and 3.3 all close when it reaches that point.

    layer.startEditing()

    context = QgsExpressionContext()
    scope = QgsExpressionContextScope()

    exp = QgsExpression(expression)
    if exp.hasParserError():
        raise Exception(exp.parserErrorString())


    for f in layer.getFeatures():
        QApplication.processEvents()
        scope.setFeature(f)
        context.appendScope(scope)

        value = exp.evaluate(context)

        computed_values[field_name].append(value)


        f.setAttribute(f.fieldNameIndex(field_name), value)

        layer.updateFeature(f)

    layer.commitChanges()

Is there any way to make it work for shapefile, or just ogr table layer?

Answer

Don't append the scope inside your loop, do it once outside the loop. Appending the scope transfers ownership of it to the context, and re-appending on the next iteration of the loop will cause undefined behaviour.