Deleting columns by indexes with PyQGIS

Question

In QGIS 3.4, I am building a model for importing and preparing multiple data by merging shapes and joining tables.

I am almost finished with the model, but I haven't found a useful tool for deleting certain columns of an attribute table in the graphical modeler.

So I am right now stuck in writing myself a tool for this purpose and unfortunately, I am not that experienced in writing code.

I need to delete the following indexes - always the same ones:

[2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,19,20,22,23,24,25,27,28,29,41,42,44,45]

My code snippet:

layer = qgis.utils.iface.activeLayer()

layer_provider.deleteAttributes([2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,19,20,22,23,24,25,27,28,29,41,42,44,45])
layer.updateFields()

I tried to make a dropdown menu using an existing code from @J.Monticolo. It did not work, as expected.

from qgis.core import QgsProcessing
from qgis.core import QgsProcessingAlgorithm
from qgis.core import QgsProcessingMultiStepFeedback
from qgis.core import QgsProcessingParameterVectorLayer
from qgis.core import QgsProcessingParameterFeatureSink
import processing


class MyModel2(QgsProcessingAlgorithm):

    def initAlgorithm(self, config=None):
        self.addParameter(QgsProcessingParameterVectorLayer('inputlayer1', 'input_layer_1', types=[QgsProcessing.TypeVector], defaultValue=None))
        self.addParameter(QgsProcessingParameterFeatureSink('Output_layer', 'output_layer', optional=True, type=QgsProcessing.TypeVectorAnyGeometry, createByDefault=True, defaultValue=None))

    def processAlgorithm(self, parameters, context, model_feedback):
        # Use a multi-step feedback, so that individual child algorithm progress reports are adjusted for the
        # overall progress through the model
        feedback = QgsProcessingMultiStepFeedback(1, model_feedback)
        results = {}
        outputs = {}

        layer=QgsVectorLayer('input_layer_1')
        with edit(layer)
            layer.deleteAttributes([2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,19,20,22,23,24,25,27,28,29,41,42,44,45])
        
        return results

    def name(self):
        return 'delete_table'

    def displayName(self):
        return 'delete_table'

    def group(self):
        return ''

    def groupId(self):
        return ''

    def createInstance(self):
        return MyModel2()

Answer 1

Try this snippet:

from qgis.core import QgsVectorLayer

layer = QgsVectorLayer(r'C:\Test\Cities.shp')

with edit(layer):
    layer.deleteAttributes([2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,19,20,22,23,24,25,27,28,29,41,42,44,45])