I'm simply reposting the code from above as an answer because I found it really useful but it took ages to find:
import_path = r"..." # Path of .mxd
export_path = r"..." # Path of output file
field_name = "Name" # Name of field used to sort DDP
mxd = arcpy.mapping.MapDocument(import_path)
for i in range(1, mxd.dataDrivenPages.pageCount + 1):
mxd.dataDrivenPages.currentPageID = i
row = mxd.dataDrivenPages.pageRow
print row.getValue(field_name)
arcpy.mapping.ExportToJPEG(mxd, export_path + "." + row.getValue(field_name) + ".jpg")
del mxd
