Re: Attribute errors occurs in objective function: AttributeError: 'generator' object has no attribute 'sense':

[Luciano Rigolin de Almeida]

Kick in the objective function some variable of the solution. You only have constants.

Luciano

Em sáb., 24 de abr. de 2021 às 20:58, Shax Studio <shakhaw...@gmail.com> escreveu:

Can someone help  me out here! As I'm pretty new here in this topics, I would love to get any suggestion from you guys.  

Thanks

from mip import Model, xsum, minimize, BINARY

c_var_i = [10,13]

y_t_i = [[1, 2, 3, 4, 5, 6], [1, 2, 3, 4, 5, 6]]

d_t = [[1, 2, 3, 4, 6, 7], [1, 2, 5, 4, 5, 4]]

k_i = [[1, 2, 3, 4, 6, 7], [1, 2, 5, 4, 5, 4]]

del_t = .25

I = range(len(y_t_i))

print(I)

J = range(len(c_var_i))

print(J)

# c_sum = [c * sum(y_t_i[i]) for i,c in enumerate(c_var_i)]

# c_sum

m = Model("Electricity Demand")

y = [[m.add_var() for i in I]]

print(y)

m.objective = minimize(c * xsum(y_t_i[i]) for i,c in enumerate(c_var_i))

*********
getting some error here:


--------------------------------------------------------------------------- AttributeError Traceback (most recent call last) <ipython-input-32-96edd6ed2f2b> in <module> 4 print(y) 5 ----> 6 m.objective = minimize(c * xsum(y_t_i[i]) for i,c in enumerate(c_var_i)) 7 ~/Library/Python/3.8/lib/python/site-packages/mip/model.py in minimize(objective) 1529 if isinstance(objective, mip.Var): 1530 objective = mip.LinExpr([objective], [1.0]) -> 1531 objective.sense = mip.MINIMIZE 1532 return objective 1533 AttributeError: 'generator' object has no attribute 'sense'


*********

m += xsum(y_t_i[i] * del_t for i in I) == [[(i * .25) for i in c] for c in d_t]

m += [[i for i in c] for c in y_t_i] <= [[i for i in c] for c in k_i]

m.optimize()

selected = [i for i in I if y[i].x >= 0.99]

print("selected items: {}".format(selected))

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[Shax Studio]

Okay. 

I'm doing now like this->

from mip import Model, xsum, minimize, BINARY

c_var_i = [10,13] # variable, production-dependent costs for power plant 𝑖 [€/𝑀𝑊h]

#y_t_i = [[1, 2, 3, 4, 5, 6], [1, 2, 3, 4, 5, 6]]

d_t = [[1, 2, 3, 4, 6, 7], [1, 2, 5, 4, 5, 4]] # demand for electricity at time t [MW]

k_i = [[1, 2, 3, 4, 6, 7], [1, 2, 5, 4, 5, 4]] # Capacity (maximum generation) of power plants

del_t = .25 # duration of time step [h]

I = set(range(len(k_i)))

print(I)

m = Model("Electricity Demand")

y_t_i = [m.add_var() for i in I] # Continous variable 

print(y_t_i)

#m.objective = minimize(c * xsum(y_t_i[i]) for i,c in zip(c_var_i, k_i))

m.objective = minimize(c * xsum(y) for c, y in zip(c_var_i, y_t_i))

[<mip.entities.Var object at 0x121341b50>, <mip.entities.Var object at 0x121341be0>]

--------------------------------------------------------------------------- AttributeError Traceback (most recent call last) <ipython-input-11-0bca49b4fe9c> in <module> 6 #m.objective = minimize(c * xsum(y_t_i[i]) for i,c in zip(c_var_i, k_i)) 7 ----> 8 m.objective = minimize(c * xsum(y) for c, y in zip(c_var_i, y_t_i)) 9 10 #m.objective = minimize([xsum(y_t_i[i]) for i in c] for c in k_i) ~/Library/Python/3.8/lib/python/site-packages/mip/model.py in minimize(objective) 1529 if isinstance(objective, mip.Var): 1530 objective = mip.LinExpr([objective], [1.0]) -> 1531 objective.sense = mip.MINIMIZE 1532 return objective 1533 AttributeError: 'generator' object has no attribute 'sense'

[Luciano Rigolin de Almeida]

Hello.

Analyzing your code better, I think you need to use m.objective as follows:

m.objective = minimize(xsum(c * y for c in c_var_i for y in y_t_i))

It is even better if you use it like this:

m.objective = minimize(xsum(c * y_t_i[i] for c in c_var_i for i in I))

The problem is in your 'c' outside of xsum.

Att,

Luciano

To view this discussion on the web visit https://groups.google.com/d/msgid/python-mip/930728ce-4071-4d6a-9cb7-6cd17feaf323n%40googlegroups.com.

[Shax Studio]

Thank you so much. But 

my approach is like getting something like 

10*(1+2+3+4+5) and 13*(1+2+3+4+5) -> this means c*sum(y[i])

[Luciano Rigolin de Almeida]

OK, but do you want to minimize which variable? Can you send your objective function?

Att,

Luciano

To view this discussion on the web visit https://groups.google.com/d/msgid/python-mip/f5ca73fb-f29e-4734-8407-d26fda8737bdn%40googlegroups.com.

[Shax Studio]

Here is my objective function

[Shax Studio]

I want to minimise Y t,i

[Chaymae Makri]

I want to ask you if you find the response to your problem because I get the same error-Python. Thanks