纸浆错误“NoneType”对象没有属性“actualSolve”

Question

我通过康达安装了纸浆和GLPk

对于p.listSolvers(onlyAvailable=True)，我看到gurobi和mosek安装为解算器：

Restricted license - for non-production use only - expires 2022-01-13
No parameters matching '_test' found
['GUROBI', 'MOSEK']

但是在执行.solve（）时，我得到以下错误：

AttributeError                            Traceback (most recent call last)
<ipython-input-19-5a6ec0364643> in <module>
----> 1 m.solve()

~/anaconda3/anaconda3/envs/isye6669/lib/python3.8/site-packages/pulp/pulp.py in solve(self, solver, **kwargs)
   1735         #time it
   1736         self.solutionTime = -clock()
-> 1737         status = solver.actualSolve(self, **kwargs)
   1738         self.solutionTime += clock()
   1739         self.restoreObjective(wasNone, dummyVar)

AttributeError: 'NoneType' object has no attribute 'actualSolve'

pulp=2.4、python=3.8.8和glpk=4.65的版本

Answer 1

您需要提供要使用的解算器。如果不提供解算器作为m.solve（）方法的参数，则pulp将使用默认值。在您的情况下，默认解算器不可用。尝试为solve方法提供GUROBI（）或MOSEK（）解算器，如下所述： https://coin-or.github.io/pulp/guides/how_to_configure_solvers.html

例如：

import pulp as pl
model = pl.LpProblem("Example", pl.LpMinimize)
solver = pl.GUROBI()
_var = pl.LpVariable('a')
_var2 = pl.LpVariable('a2')
model += _var + _var2 == 1
result = model.solve(solver)