How to dynamically get the value of a variable in pyfmi

For example, this is my modelica model

model Test
  Real x(start = 1000);
  input Real k;
equation 
  der(x) = -k * x;
end Test;

from pyfmi import load_fmu

model = load_fmu('D:/FMU/Test.fmu')
model.initialize(0,10)

def f(time):
    global model
    x = model.get('x')
    return time*0.1

inputs = ('k', f)
result = model.simulate(final_time=10, input=inputs)

How can I get the value of x in function f，or how can I get the value of the current state and then adjust the input parameters to continue the simulation? I tried to get it via model.get(), but failed. Thanks a lot for your help！

I would like to reframe your question a little bit as follows:

1. Make simulation 1 and get the final value x and call it x1
2. Reset (or reload) the model
3. Enter the initial value of x as x1
4. Optionally change the parameter k
5. Make simulation 2 and get the final value x and call it x2
6. Plot the two simulations after each other

The model I change to this

model Test
  parameter Real k = 10;
  parameter Real x_start = 1000;
  Real x(start=x_start, fixed=true);  
equation
  der(x) = -k*x;
end Test;

And the script to this (and I use deprecated JModelica compiler to make the FMU, but instead the FMU can be made by for instance OpenModelica ver 1.25 or later)

# Setup framework
from pymodelica import compile_fmu 
from pyfmi import load_fmu
import matplotlib.pyplot as plt

# Compile model
fmu_model = compile_fmu('Test','Test.mo', target='cs')

# Load model
model = load_fmu(fmu_model)

# Simulate
result1 = model.simulate(start_time=0, final_time=1)
x1 = model.get('x')

model.reset() 
model.set('k', 1)
model.set('x_start',x1)
result2 = model.simulate(start_time=1, final_time=2)
x2 = model.get('x')

# Plot results
plt.figure()
plt.semilogy(result1['time'], result1['x'])
plt.semilogy(result2['time'], result2['x'])
plt.xlabel('Time'); plt.ylabel('x'); plt.grid()
plt.show()

Hope this address your main question?

Note, that the method can be easily generalised for continuous time systems. A dictionary of all the continuous time states can be obtained by the PyFMI-command

model.get_states_list()

For further inspiration on how to handle the more general case, take a look at the example on my Github page

https://colab.research.google.com/github/janpeter19/BPL_TEST2_Batch/blob/main/BPL_TEST2_Batch_colab.ipynb

run the example, and in cell 17 you see application of continued simulation after a parameter change. Also take a look at the Python setup file BPL_TEST2_Batch_explore.py where you find the code for simu(,'cont').

Here is in the FMI-standard a procedure to get and set the total state of an FMU, i.e. including both continuous and discrete time states and more.

model.get_fmu_state()
model.set_fmu_state()

However, the FMUs generated by OpenModelica (or deprecated JModelica) does not support this functionality. Therefore, the approach described above has a place.