AttributeError: 'Series' object has no attribute 'is_expression_type'

[Armaghan Bhr]

Enter code here...

I'm trying to calculate the temperature along a pipeline by using 2 for loops, one for time and one for different points along the pipe. and finally, I get (return) the outlet temperature of the pipe (which is at n_nodes=2500000 or the last point in self.block.all_x)
This is a part of my code:

            self.block.all_time = Set(initialize=range(n_steps), ordered=True)
            self.block.all_x = Set(initialize=range(1, self.n_nodes + 1), ordered=True)

Then I've defined the variables as:

self.block.temperature_out_cv = Var(lines, self.block.all_time, self.block.all_x)




And finally, we have the calculation of the temperatures at different times:

            for j in self.block.all_x:
                def _bc_temp_out(b, l, t):
                    if mass_flow.all() == 0:
                        return Constraint.Skip
                    elif t == 0:
                        return b.temperature_out_cv[l, t, j] == float(self.params['temperature_init_cv_' + l].v())
                    else:
                        for i in range(t+1):
                            if i == 0:
                                b.temperature_out_cv[l, i, j] = float(self.params['temperature_init_cv_' + l].v())
                            else:
                                if j == 1:
                                    return b.temperature_out_cv[l, i, j] == (b.temperature_out_cv[l, i - 1, j] + b.u[
                                        i] * time_step / self.params['delta_x'].v() * b.temperatures[l, i]
                                                                     + time_step / Z * Tg[i]) / (
                                                                            1 + b.u[i] * time_step / self.params[
                                                                        'delta_x'].v()
                                                                            + time_step / Z)
                                else:
                                    return b.temperature_out_cv[l, i, j] == (b.temperature_out_cv[l, i - 1, j] + b.u[
                                        i] * time_step / self.params['delta_x'].v() * b.temperature_out_cv[
                                                                         l, i, j - 1]
                                                                     + time_step / Z * Tg[i]) / (
                                                                            1 + b.u[i] * time_step / self.params[
                                                                        'delta_x'].v()
                                                                            + time_step / Z)

                self.block.add_component('_bc_temp_out' + str(j), Constraint(lines, self.block.all_time, rule=_bc_temp_out))

but I get the error below:

ERROR: Rule failed when generating expression for constraint
  File "C:\Users\Armaghan Bhr\Anaconda3\envs\dhopt\lib\site-packages\pyomo\core\base\constraint.py", line 779, in construct
    bbThor._bc_temp_out1 with index ('supply', 1): AttributeError: 'Series'
    ndx)
    object has no attribute 'is_expression_type'
ERROR: Constructing component 'bbThor._bc_temp_out1' from data=None failed:
  File "C:\Users\Armaghan Bhr\Anaconda3\envs\dhopt\lib\site-packages\pyomo\core\base\misc.py", line 57, in apply_indexed_rule
    return rule(model, *index)
  File "C:\Users\Armaghan Bhr\Desktop\modesto-master\modesto\pipe.py", line 1723, in _bc_temp_out
    AttributeError: 'Series' object has no attribute 'is_expression_type'
    + time_step / Z * Tg[i]) / (
  File "C:\Users\Armaghan Bhr\Anaconda3\envs\dhopt\lib\site-packages\pyomo\core\expr\numvalue.py", line 772, in __add__
    return _generate_sum_expression(_add,self,other)
  File "C:\Users\Armaghan Bhr\Anaconda3\envs\dhopt\lib\site-packages\pyomo\core\expr\numeric_expr.py", line 1720, in _generate_sum_expression
    if not (_other.__class__ in native_types or _other.is_expression_type()):
  File "C:\Users\Armaghan Bhr\Anaconda3\envs\dhopt\lib\site-packages\pandas\core\generic.py", line 5179, in __getattr__
    return object.__getattribute__(self, name)
AttributeError: 'Series' object has no attribute 'is_expression_type'

while time_step and Z are constant and Tg[i] is a pandas series. I've also printed these 3 parameters but still get the same error.

[Armaghan Bhr]

I should mention that time_step and Z are constant and Tg[i] is a pandas series

[Nicholson, Bethany L.]

You can't use a Pandas Series object directly in a Pyomo expression. You have to extract the desired constant value from the Series.

Bethany

---

From: pyomo...@googlegroups.com <pyomo...@googlegroups.com> on behalf of Armaghan Bhr <armaghan...@gmail.com>
Sent: Thursday, April 23, 2020 10:50 AM
To: Pyomo Forum
Subject: [EXTERNAL] AttributeError: 'Series' object has no attribute 'is_expression_type'

 

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[Armaghan Bhr]

Thanks for your reply!

but that's what I did. Here the Tg parameter is defined:

def create_params(self):
	params = Component.create_params(self)
	params.update({
	'diameter': DesignParameter('diameter',
	'Pipe diameter',
	'DN (mm)', mutable=True),
	'Tg': WeatherDataParameter('Tg',
	'Undisturbed ground temperature',
	'K')})

Then I extract the constant value from series:

Tg = self.params['Tg'].v() # ground temperature (T_out in equation 4)

Also in order to set up the main model, we have:

time_index = pd.DatetimeIndex(start=start_time, freq=str(time_step) + 'S', periods=n_steps)
# Ground temperature
t_g = pd.Series(12 + 273.15, index=t_amb.index)

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