GPencil: Scripting weight_get and Vertex Groups not working at expected with several groups #91511

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 960M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 391.25

Blender Version
Broken: version: 2.93.1, branch: master, commit date: 2021-06-22 05:57, hash: 1b8d33b18cGreasepencil weight_get and vertex_group.blend

Short description of error

weight_get will result in a vertex_group index error (RuntimeError: Error: Groups: index out of range) even when the stroke is weight-painted completely
Running weight_set along stroke first, weight-painting manually, and then running weight_get will not throw the error (most of the time).
The vertex_group index property of weight_get will result in a (RuntimeError: Error: Groups: index out of range) if a lower vertex_group index property had resulted in an index out of range error.

Exact steps for others to reproduce the error
See attached blend.

I've included 3 examples:
A try and except script to get the vertex weight of 4 strokes which fails on 3 upper vertex group indices.
A script that sets the vertex weight of all points to 0 and after which when you weight paint manually and rerun the first script, you get the vertex weight successfully
A script where you create the vertex_group and set them with a specific value successfully, but when you try to read them back with weight_get, it results with a vertex group index out of range

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 960M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 391.25 **Blender Version** Broken: version: 2.93.1, branch: master, commit date: 2021-06-22 05:57, hash: `1b8d33b18c`[Greasepencil weight_get and vertex_group.blend](https://archive.blender.org/developer/F10481110/Greasepencil_weight_get_and_vertex_group.blend) **Short description of error** - weight_get will result in a vertex_group index error (RuntimeError: Error: Groups: index out of range) even when the stroke is weight-painted completely - Running weight_set along stroke first, weight-painting manually, and then running weight_get will not throw the error (most of the time). - The vertex_group index property of weight_get will result in a (RuntimeError: Error: Groups: index out of range) if a lower vertex_group index property had resulted in an index out of range error. **Exact steps for others to reproduce the error** See attached blend. I've included 3 examples: A try and except script to get the vertex weight of 4 strokes which fails on 3 upper vertex group indices. A script that sets the vertex weight of all points to 0 and after which when you weight paint manually and rerun the first script, you get the vertex weight successfully A script where you create the vertex_group and set them with a specific value successfully, but when you try to read them back with weight_get, it results with a vertex group index out of range

Added subscriber: @kluya

Added subscriber: @antoniov

Changed status from 'Needs Triage' to: 'Confirmed'

The problem is checking the number of available weights.

This issue was referenced by cc31c159a1

This issue was referenced by cc31c159a1501b25df014a9b39b720e4ef8d53b3

This issue was referenced by 1f51672d71

This issue was referenced by 1f51672d7126d8c0a0b962060c01632e6e07dd5f

Changed status from 'Confirmed' to: 'Resolved'

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GPencil: Scripting weight_get and Vertex Groups not working at expected with several groups #91511