Map Document properties

Summary

When used with the Describe function, a map document returns a Describe dataType property that returns a value of "MapDocument".

Map document properties example

The following stand-alone script displays use of Describe with an .mxd file:

import arcpy

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