Changing feature class and field aliases in bulk using ArcPy?

With help from Mark Cederholm I have a working solution using python and arcobjects. It's rough around the edges, but it got the job done. After following the recipe on that page, create a new script which uses the GetLibPath, NewObj, CType, OpenFeatureClass functions from snippets.py. Also create the rename lookup tables in .csv format:

Field to Field Alias lookup (att_code-name_lookup.csv):

Attrib_Name,Alias_Name
CODE,Specification Code
VALDATE,Validity Date
...

Feature class to FC Alias lookup (fc_code-name_lookup.csv):

"FC_Name","AliasName"
"BS_1250009_0","Navigational Aid"
"BS_1370009_2","Residential Area"
...

and the script:

import sys
sys.path.append('k:/code')
from snippets import GetLibPath, NewObj, CType, OpenFeatureClass
sWorkingDir = "k:/code/"
sFileGDB = sWorkingDir + "blank_canvec.gdb"
sResourceDir = "k:/code/"
sFCAliasFile = sResourceDir + "fc_code-name_lookup.csv"
sAttAliasFile = sResourceDir + "att_code-name_lookup.csv"
sProduct = "ArcEditor"

def BuildFieldAliasLookup():
    lookup = {}
    f = open(sAttAliasFile, "r")
    bFirst = True
    for line in f:
        # Skip first line
        if bFirst:
            bFirst = False
            continue
        sTokens = line.replace('"','').split(',')
        sFieldName = sTokens[0]
        sAlias = sTokens[1]
        lookup[sFieldName] = sAlias
    return lookup

def AlterAlias():
    # Initialize
    from comtypes.client import GetModule
    import arcgisscripting
    sLibPath = GetLibPath()
    GetModule(sLibPath + "esriGeoDatabase.olb")
    GetModule(sLibPath + "esriDataSourcesGDB.olb")
    import comtypes.gen.esriGeoDatabase as esriGeoDatabase
    gp = arcgisscripting.create(9.3)

    try:
        gp.setproduct(sProduct)
    except:
        gp.AddMessage(gp.GetMessages(2))

    # Build field alias lookup table
    AttrLookup = BuildFieldAliasLookup()
    # Open alias file and loop through lines
    f = open(sFCAliasFile, "r")
    bFirst = True
    for line in f:
        # Skip first line
        if bFirst:
            bFirst = False
            continue
        sTokens = line.replace('"','').split(',')
        sFCName = sTokens[0]
        sAlias = sTokens[1]
        print "Processing: ", sFCName
        # Open feature class
        try:
            pFC = OpenFeatureClass(sFCName)
        except:
            print "Could not open ", sFCName
            continue
        # Alter feature class alias
        try:
            pSE = CType(pFC, esriGeoDatabase.IClassSchemaEdit)
            pSE.AlterAliasName(sAlias)
        except:
            print "Error altering class alias"
            continue
        # Alter field aliases
        try:
            for sKey in AttrLookup.keys():
                i = pFC.FindField(sKey)
                if i == -1:
                    continue
                sAlias = AttrLookup[sKey]
                pSE.AlterFieldAliasName(sKey, sAlias)
        except:
            print "Error altering field aliases"
    print "Done."

print 'Field <--> Alias lookup table is:', BuildFieldAliasLookup()
print AlterAlias()

As of version 10.1 AlterAliasName() can be used to re-alias tables:

table = r"C:\path\to\connection.sde\OWNER.TABLE"
arcpy.AlterAliasName(table, "table_alias")

As of version 10.3 Alter Field can be used to re-alias fields:

table = r"C:\path\to\connection.sde\OWNER.TABLE"
arcpy.AlterField_management(table, "FIELD_NAME", new_field_alias="field_alias")

This code works for me in 9.3.1 ...

public static void TestAlterAlias(IApplication app)
{
    // make a dictionary of old/new names
    Dictionary<string, string> nameDict = new Dictionary<string, string>(StringComparer.CurrentCultureIgnoreCase);
    nameDict.Add("qsectionalias", "qsectionalias2");
    nameDict.Add("sursysalias", "sursysalias2");
    string[] directories =  System.IO.Directory.GetDirectories(@"D:\Projects\EmpireOil\data",@"*.gdb",
        System.IO.SearchOption.TopDirectoryOnly);
    foreach(string dir in directories)
    {
        List<IName> fcnames = GetFCNames(dir);
        foreach (IName fcName in fcnames)
        {
            ChangeFieldAliases(fcName, nameDict);
        }
    }
}

public static void ChangeFieldAliases(IName fcName, Dictionary<string, string> aliasDict)
{
    IFeatureClass fc = (IFeatureClass)fcName.Open();
    IClassSchemaEdit3 cse = (IClassSchemaEdit3)fc;
    ((ISchemaLock)fc).ChangeSchemaLock(esriSchemaLock.esriExclusiveSchemaLock);
    SortedList<string, string> changeList = new SortedList<string, string>();
    for (int i = 0; i < fc.Fields.FieldCount; i++)
    {
        string fldName = fc.Fields.get_Field(i).Name;
        string alias = fc.Fields.get_Field(i).AliasName;
        if (aliasDict.ContainsKey(alias))
        {
            changeList.Add(fldName, aliasDict[alias]);
            // set it blank for now, to avoid problems if two fields have same aliasname.
            cse.AlterFieldAliasName(fldName, "");
        }
    }

    // change the alias
    foreach (KeyValuePair<string, string> kvp in changeList)
        cse.AlterFieldAliasName(kvp.Key, kvp.Value);
    ((ISchemaLock)fc).ChangeSchemaLock(esriSchemaLock.esriSharedSchemaLock);
}

public static List<IName> GetFCNames(string wsPath)
{
    List<IName> names = new List<IName>();
    IWorkspaceFactory wsf = new ESRI.ArcGIS.DataSourcesGDB.FileGDBWorkspaceFactoryClass();
    IWorkspace ws = wsf.OpenFromFile(wsPath, 0);
    IEnumDatasetName enumName = ws.get_DatasetNames(esriDatasetType.esriDTAny);
    enumName.Reset();
    IDatasetName dsName = null;
    while ((dsName = enumName.Next()) != null)
    {
        if(dsName is IFeatureClassName)
            names.Add((IName)dsName);
        else if(dsName is IFeatureDatasetName)
        {
            IEnumDatasetName enumName2 = dsName.SubsetNames;
            enumName2.Reset();
            IDatasetName dsName2;
            while((dsName2=enumName2.Next())!= null)
            {
                if(dsName2 is IFeatureClassName)
                    names.Add((IName)dsName2);
            }
        }
    }
    return names;
}