If your fGDB actually does have feature datasets (not just top-level feature classes), you could do:
import arcpy
import os
arcpy.env.workspace = r"X:\311\Obtaining GIS Data\TaxParcels.gdb"
# Get top-level feature classes
featureclasses = arcpy.ListFeatureClasses()
# Get data-set feature classes
datasets = arcpy.ListDatasets()
for ds in datasets:
featureclasses.extend(arcpy.ListDatasetsListFeatureClasses(feature_dataset=ds))
for fc in featureclasses:
print(fc)
Otherwise, if your fGDB does not have feature datasets (or if you're not interested in the feature classes within feature datasets), then it would simply be:
import arcpy
import os
arcpy.env.workspace = r"X:\311\Obtaining GIS Data\TaxParcels.gdb"
featureclasses = arcpy.ListFeatureClasses()
for fc in featureclasses:
print(fc)