LUT1D block fails with len() of unsized object in PathSim 0.23.2

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Description

Environment

• Python: 3.14
• NumPy: 1.18.0
• SciPy: 2.5.1
• PathSim: 0.23.2
• PathView: latest local version

Problem

I found a reproducible issue with the LUT1D block in PathSim 0.23.2.

When I run a model containing a LUT1D block, the simulation fails with:

TypeError: len() of unsized object

The failure occurs even when the LUT1D block has no input connection.

For example:

lut1d = LUT1D(
    points=[0, 100],
    values=[0, 100],
    fill_value="extrapolate"
)

Running a model containing only this block produces:

Streaming simulation failed: len() of unsized object

By comparison, a model containing only a Constant block runs successfully.

Investigation

I checked the installed PathSim source code.

PathSim reports:

0.23.2
<class 'pathsim.blocks.table.LUT1D'>
C:\...\site-packages\pathsim\blocks\table.py

The LUT1D implementation uses SciPy's interp1d:

self.inter = interp1d(
    self.points,
    self.values,
    fill_value=fill_value
)

and its function is:

def func(*x):
    return self.inter(x[0])

LUT1D inherits from Function, whose implementation evaluates the function using:

self.op_alg = Operator(func=lambda x: func(*x))

I also inspected the runtime input representation. The Function block's input array can be represented as a NumPy ndarray, for example:

<class 'numpy.ndarray'>
[0.]

The error message suggests that a scalar / 0-D NumPy value may be reaching interp1d in some execution path.

Reproduction

A minimal model containing only:

LUT1D

with:

points = [0, 100]
values = [0, 100]
fill_value = "extrapolate"

is sufficient to reproduce the error in my environment.

Adding a Constant and connecting:

Constant → LUT1D

also reproduces the same error.

Expected behavior

I would expect LUT1D to accept scalar input values and perform the interpolation without raising an exception.

Question

Could you please check whether this is a bug in the LUT1D / Function implementation in PathSim 0.23.2?

In particular, could the input passed to:

self.inter(x[0])

sometimes be a 0-D NumPy array or scalar?

If so, would explicit scalar/array handling before calling interp1d be an appropriate fix?

Thank you for your help.

Steps to Reproduce

1. Open PathView with PathSim 0.23.2.
2. Create a Constant block with value = 50.
3. Create a LUT1D block with:
   points = [0, 100]
   values = [0, 100]
   fill_value = "extrapolate"
4. Connect the Constant output to the LUT1D input.
5. Run the simulation.
6. The simulation fails immediately with:

TypeError: len() of unsized object

The simulation stops with:

FINISHED -> STREAMING (total steps: 0, successful: 0)

Expected Behavior

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Version

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Browser

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Additional Context

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