Python and comtypes: read map document layers and .lyr files with ArcObjects

read_lyrs.py

from comtypes.client import GetModule, CreateObject
from snippets102 import GetStandaloneModules, InitStandalone

GetStandaloneModules()
InitStandalone()

esriCarto = GetModule(r"C:\Program Files (x86)\ArcGIS\Desktop10.4\com\esriCarto.olb")

layerFile = CreateObject(esriCarto.LayerFile,interface=esriCarto.ILayerFile)
lyrs = ["C:\GIS\Temp\lyrs_remote_sde_many_features\c123.lyr",
        r"C:\GIS\Temp\lyrs_local_sde\Park_boundary.lyr",
        "C:\GIS\Temp\lyrs_remote_sde_few_features\Data.lyr"]

for lyr_file in lyrs:
    layerFile.Open(lyr_file)
    lyr = layerFile.Layer
    desc = lyr.QueryInterface(esriCarto.IFeatureLayer)
    print desc.DataSourceType
    #u'SDE Feature Class'
    print desc.FeatureClass.AliasName

read_lyrs_in_mxd.py

pMapDocument = snippetarcgis102.NewObj(esriCarto.MapDocument,esriCarto.IMapDocument)
pMapDocument.open(path) #like pDoc
pMap = pMapDocument.Map(0)
pEnumLayer = pMap.Layers(None,True)
#key = name of layer from gdb (en UPPER CASE) value =ptr to IGeoFeatureLayer layers (not group layers)
layer_ptr_dict={}

pLayer = pEnumLayer.Next()
while pLayer:
    pGeoFeatureLayer = snippetarcgis102.CType(pLayer,esriCarto.IGeoFeatureLayer)
    if pGeoFeatureLayer: # list of IGeofeature layers (not group layers)
        en_name = pGeoFeatureLayer.FeatureClass.AliasName.encode('utf-8') # name in GDB, not in TOC
        layer_ptr_dict [en_name] = pGeoFeatureLayer
    else: # else it is group layer and we collapse it
        group_layer =  snippetarcgis102.CType(pLayer,esriCarto.IGroupLayer)
        group_layer.Expanded = False #collapse group layers
    pLayer = pEnumLayer.Next()