This script runs through your glyphs and outputs two classes for use in your GDEF table. Open for suggestions.

printGDEF.py

# Find glyphs with anchors and _anchors,
# to properly populate a GDEF table.

f = CurrentFont()

# Sort alphabetically for easier scanning
names = f.keys()
names.sort()

gdef_base = '@BASE = [ '
gdef_combining = '@COMBINING_MARKS = [ '

for n in names:
    g = f[n] # Reset glyph object
    anchors = [] # If it’s an array, it’s easier to do logic
    for a in g.anchors:
        anchors.append(a.name)
    for a in g.anchors:
        if a.name.startswith("_"):
            # If any of the anchors start with an underscore,
            # it’s a combining mark
            gdef_combining += g.name + ' '
            break
    if g.anchors:
        # If a glyph has anchors, AND
        for a in g.anchors:
            if not a.name.startswith("_"):
                # it has NO anchors starting with an underscore,
                # then it’s a base glyph
                gdef_base += g.name + ' '
            break

print gdef_base + '];'
print gdef_combining + '];'