[英]Python - Using an array index that depends on an input value
I am trying to write a mathematical program in a program called pyomo (a python library). 我正在尝试在名为pyomo(Python库)的程序中编写数学程序。 Below, model is an object I declared already, BRANCH
is a set; 下面,模型是我已经声明的对象, BRANCH
是集合; model.branch_scpt
, model.M
, model.branch_tbus
, and model.branch_fbus
are all parameter lists that are loaded as input when the code executes (They all have dimension = BRANCH). model.branch_scpt
, model.M
, model.branch_tbus
和model.branch_fbus
都是在代码执行时作为输入加载的参数列表(它们的维数均为BRANCH)。 Additionally, model.bus_angle
, model.line_flow
, and model.z_line
are lists of decision variables (all also of dimension BRANCH). 此外, model.bus_angle
, model.line_flow
和model.z_line
是决策变量的列表(所有维度均为BRANCH)。 This is the definition of one of my constraint types, where j
is in BRANCH
: 这是我的一种约束类型的定义,其中j
在BRANCH
:
def Line_FlowA_rule(model,j):
return ( model.branch_scpt[j]*( model.bus_angle[model.branch_tbus[j]]
- model.bus_angle[model.branch_fbus[j]] )
- model.line_flow[j] + (1 - model.z_line[j]) * model.M[j] >= 0 )
model.Line_FlowA = Constraint(model.BRANCH, rule=LineFlowA_rule)
Notice that the element model.bus_angle[j]
referenced in constraint Line_FlowA[j]
depends on the element that model.branch_tbus[j]
returns (similarly, the element that model.branch_fbus[j]
returns). 注意,元件model.bus_angle[j]
在约束中引用Line_FlowA[j]
依赖于元件上model.branch_tbus[j]
返回(类似地,元素model.branch_fbus[j]
返回)。 However, model.branch_tbus[j]
is a data input value and I believe this is what is causing the following error: 但是, model.branch_tbus[j]
是数据输入值,我相信这是导致以下错误的原因:
"Unexpected exception while running model arpatest_nbp_constraint.py
Unable to index variable bus_angle using supplied index with unhashable type: '_ParamValue'"
In order to make the function neater, I tried to redefine the function as follows: 为了使功能更整洁,我尝试如下重新定义功能:
def Line_FlowA_rule(model,j):
t = model.branch_tbus[j]
f = model.branch_fbus[j]
return ( model.branch_scpt[j]*( model.bus_angle[f]
- model.bus_angle[t] )
- model.line_flow[j] + (1 - model.z_line[j]) * model.M[j] >= 0 )
model.Line_FlowA = Constraint(model.BRANCH, rule=Line_FlowA_rule)
but I obtained the same error. 但是我得到了同样的错误。
Lastly, to convert the values t and f into immutable types I tried: 最后,我尝试将值t和f转换为不可变的类型:
def Line_FlowA_rule(model,j):
t = tuple(model.branch_tbus[j])
f = tuple(model.branch_fbus[j])
return ( model.branch_scpt[j]*( model.bus_angle[f]
- model.bus_angle[t] )
- model.line_flow[j] + (1 - model.z_line[j]) * model.M[j] >= 0 )
model.Line_FlowA = Constraint(model.BRANCH, rule=Line_FlowA_rule)
This led to the error: 这导致了错误:
ERROR: Unexpected exception while running model arpatest_nbp_constraint.py
'_ParamValue' object is not iterable
Can anyone please tell me what I am doing wrong here? 有人可以告诉我我在做什么错吗? I am new to python so it is probably something basic. 我是python的新手,所以它可能是基本的东西。 Thanks a lot 非常感谢
Furst time seeing this, but inptecting the source, we can see, that class _ParamValue
defined here is extending class NumericConstant
, defined here , from code we can learn there is attribute value
, so the only thing i can suggest is to change code something like that: 弗斯特一次看到这一点,但inptecting源,我们可以看到, class _ParamValue
定义在这里被扩展class NumericConstant
,定义在这里 ,从代码中我们可以得知有属性value
,所以我可以建议的唯一的事情就是改变代码类似那:
def Line_FlowA_rule(model,j):
t = model.branch_tbus[j].value
f = model.branch_fbus[j].value
return ( model.branch_scpt[j]*( model.bus_angle[f]
- model.bus_angle[t] )
- model.line_flow[j] + (1 - model.z_line[j]) * model.M[j] >= 0 )
model.Line_FlowA = Constraint(model.BRANCH, rule=Line_FlowA_rule)
But that can work of course if those parameters are holding indexes for other parameters. 但是,如果那些参数保存着其他参数的索引,那当然可以工作。
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