import os
from collections import defaultdict
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")

#----------------------------------------------------------------------
def update_mxd_layers_field_aliases(mxd_path,output_mxd_path=None):
    """update field aliases for layers in a map document based on the field aliases stored in geodatabase"""
    pMapDocument = CreateObject(esriCarto.MapDocument, interface=esriCarto.IMapDocument)
    pMapDocument.Open(mxd_path)
    pMap = pMapDocument.Map(0)
    pEnumLayer = pMap.Layers(None,True)
    pLayer = pEnumLayer.Next()

    source_aliases = defaultdict(list)
    edited_aliases = defaultdict(list)

    while pLayer:
        print "Layer: ", pLayer.Name
        fields = pLayer.QueryInterface(esriCarto.ILayerFields)

        for i in xrange(fields.FieldCount):
            print "Name:", fields.Field(i).name, "Alias:", fields.FieldInfo(i).alias
            source_aliases[pLayer.Name].append((fields.Field(i).Name,fields.FieldInfo(i).alias))
            fields.FieldInfo(i).alias = fields.Field(i).AliasName
            edited_aliases[pLayer.Name].append((fields.Field(i).Name,fields.Field(i).AliasName))

        pLayer = pEnumLayer.Next()

    if not output_mxd_path:
        output_mxd_path = os.path.join(os.path.dirname(mxd_path),os.path.splitext(os.path.basename(mxd_path))[0] + '_upd' +
                                       os.path.splitext(os.path.basename(mxd_path))[1])

    pMapDocument.SaveAs(output_mxd_path)
    return (source_aliases,edited_aliases)

mxd_path = r"C:\GIS\Temp\alias_mxd.mxd"
print update_mxd_layers_field_aliases(mxd_path)