Map Document properties

Résumé

When used with the Describe function, a Map Document returns a dataType of "MapDocument".

Map Document properties example (stand-alone script)

The following stand-alone script displays use of Describe with a .mxd

import arcpy

map_document = r"C:\Project\Project.mxd"
desc = arcpy.Describe(map_document)
print(desc.datatype)  # MapDocument