# Simulation Parameters Initialization setting

**URL:** <https://forum.plexim.com/t/simulation-parameters-initialization-setting/3112>\
**Category:** PLECS\
**Tags:** octave, python\
**Created:** [May 28, 2026, 2:58am UTC](https://forum.plexim.com/t/simulation-parameters-initialization-setting/3112 "2026-05-28T02:58:15Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![ziguin](https://avatars.discourse-cdn.com/v4/letter/z/839c29/32.png) [@ziguin](https://forum.plexim.com/u/ziguin)\
**Post date:** [May 28, 2026, 2:58am UTC](https://forum.plexim.com/t/simulation-parameters-initialization-setting/3112/1 "2026-05-28T02:58:15Z")

</div>

Hello,

I have a few questions regarding the use of XML-RPC and `ModelVars` in PLECS.

1. In the “Simulation Parameters” → “Initialization” tab, variables can be defined manually.  
If a variable with the same name is also provided through Python using `ModelVars` via XML-RPC, which one takes priority?

2. I set the block parameter name as `fs`, and then assigned `fs` through `ModelVars` in Python. However, during simulation I received the following error saying that `fs` is undefined:

```bash
2026-05-28 11:29:22 [ERROR] [Error in simulate: <Fault -34000: "Simulation error: Error while executing callback for parallel simulation 1:
Error: Error in component 'sepic_no_under_cpp/PI_Digital2/Delay' while evaluating parameter 'Sample time (s)': 'fs' undefined.">] 
 [{'ModelVars': {'L1': 0.00022, 'L2': 2.5e-05, 'fs': 55600.0}}]

```

In this case, are there certain blocks that cannot access variables provided through `ModelVars`?

1. When using:

```python
plecs = xml.Server("http://localhost:1080/RPC2").plecs

```

is there a way to view the available functions, APIs, or internal arguments provided by `plecs` so that I can use them more effectively?

Thank you for your help.

---

<div class="post-metadata">

**Author:** ![Bryan\_Lieblick](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/bryan_lieblick/32/10_2.png) [@Bryan\_Lieblick](https://forum.plexim.com/u/Bryan_Lieblick)\
**Post date:** [May 28, 2026, 6:09pm UTC](https://forum.plexim.com/t/simulation-parameters-initialization-setting/3112/2 "2026-05-28T18:09:59Z")

</div>

Can you post a simple model and your script? I suspect the issue is due to the [variable scope in your masked subsystem](https://docs.plexim.com/plecs/latest/using-plecs/masking-subsystems/#mask-workspace), but a model is required to fully diagnose.

> Is there a way to view the available functions, APIs, or internal arguments provided by `plecs` so that I can use them more effectively?

The API is [documented in the user manual](https://docs.plexim.com/plecs/latest/scripting/#rpc-interface-in-plecs-standalone) as well as relevant helpful demo models. If you are using XML-RPC, then the supported methods are accessible with the following, noting that the documentation here is thin and the user manual should be used for a more comprehensive reference.

```auto
import xmlrpc.client
proxy = xmlrpc.client.ServerProxy("http://localhost:1080")
proxy.system.listMethods()
>> ['system.listMethods', 'plecs.set', 'plecs.getModelTree', 'plecs.close', 'plecs.statistics', 'system.methodHelp', 'plecs.scope', 'plecs.analyze', 'plecs.load', 'plecs.codegen', 'plecs.simulate', 'plecs.webserver', 'plecs.get']

```