dump all vertex group weights of Blender mesh objects to CSV.

wdump.py

# MIT License
#
# Copyright (c) 2026 nobiru
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the “Software”), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

# dump all vertex group weights of Blender mesh objects to CSV.
# format: collection_name, object_name, vert_index, vert_group_name, vert_group_weight, weight_zero_flag

import sys
import csv
import bpy

WEIGHT_ZERO = "_WeightZero_"

def main():
    dump_weights("weights.csv")

def dump_weights(fpath = None):
    f = sys.stdout

    if fpath:
        try:
            f = open(fpath, "w", newline = "", encoding = "utf-8")
        except:
            f = sys.stdout

    writer = csv.writer(f);
    writer.writerow(["collection", "object", "v.index", "group", "weight"])

    for c in bpy.data.collections:
        for o in c.objects:
            if o.type != 'MESH':
                continue

            for v in o.data.vertices:
                if v.groups:
                    for g in v.groups:
                        gname = o.vertex_groups[g.group].name
                        wz = WEIGHT_ZERO if (g.weight == 0 and len(v.groups) == 1) else ""
                        writer.writerow([c.name, o.name, v.index, gname, g.weight, wz])
                else:
                    writer.writerow([c.name, o.name, v.index, "None", "None", WEIGHT_ZERO])

    if f is not sys.stdout:
        f.close()

if __name__ == "__main__":
    main()