错误:无法将序列乘以'Mul'类型的非整数 [英] Error : Can't multiply sequence by non-int of type 'Mul'

问题描述

我在下面定义了一种方法，该方法假定将5个整数/浮点值作为输入，并使用一个列表对象(lst参数)，并且仅返回方程式F中r的正解. F的公式应返回一个列表，其中使用给定的方程对每个元素进行乘/减.

I defined a method below that is supposed to take 5 integer/float values as input, and one list object (the lst parameter) and return only the positive solutions for r in the equation F. The formula for F should return a list where each element is multiplied/subtracted using the equation given.

我收到了上面提到的错误Error : Can't multiply sequence by non-int of type 'Mul'.我想念什么?

I got the error Error : Can't multiply sequence by non-int of type 'Mul' mentioned above. What am I missing?

from sympy import *
from math import pi
class solarheating:

    def circular_rr(T0,T,lst,m,Cp,Eg):

        r = var('r')
        F = T0+pi*r**2*Eg/(m*Cp)*lst-T
        r = solve(F,r)

        return r[1]

    lst = [0,0.25,0.5,0.75,1.0,1.25]   
    a = circular_rr(20,15,lst,.24,4.2,.928)
    print(a)

推荐答案

您忘记将在其上调用代码的对象(或self)的实例传递给方法.由于没有self，因此会出现非整数错误，因为T0变为self，T变为T0，然后将您的lst用作T.由于您不能从列表中减去int，因此会产生错误.

You forgot to pass the instance of the object (or self) on which the code is being called to the method. Since there was no self, you were getting the non-int error, because T0 became self, T became T0, and then your lst was being used as T. Since you cannot subtract a int from a list, this produced an error.

这是更正的代码.

from sympy import *
from math import pi

class solar heating:

    def circular_rr(self,T0,T,lst,m,Cp,Eg):
        r = var('r')
        F = T0+pi*r**2*Eg/(m*Cp)*lst-T
        r = solve(F,r)    
        return r[1]

lst = [0,0.25,0.5,0.75,1.0,1.25]   
my_instance = solarheating()
a = my_instance.circular_rr(20,15,lst,.24,4.2,.928)
print(a)

您需要使用self的原因是因为Python不使用@syntax来引用实例属性.在您通过self属性传递的实例上调用该方法.您实际上并没有在Python中编写实例方法.您编写的是(必须)将实例作为第一个参数的类方法.因此，您必须将实例参数明确地放置在某个地方.

The reason you need to use self is because Python does not use the @syntax to refer to instance attributes. The method is called on the instance you pass in the self attribute. You don't actually write instance methods in Python; what you write is class methods which (must) take an instance as a first parameter. And therefore, you’ll have to place the instance parameter somewhere explicitly.

除了上面已经描述的明显的self错误之外，您还需要将浮点数乘以一个列表.这就是导致can't multiply sequence by non-int of type 'Mul'错误的原因.

Besides the obvious self error I've described above, you're multiplying a float by a list. That's what's causing the can't multiply sequence by non-int of type 'Mul' error.

如果要将列表中的每个项目乘以浮点数，则更正后的方法代码将为:

If you want to multiply each item in the list by the float, your corrected method code will be:

    def circular_rr(self,T0,T,lst,m,Cp,Eg):
        r = var('r')
        temp_val = T0+pi*r**2*Eg/(m*Cp)
        F = [x*temp_val-T for x in lst]
        r = solve(F,r)    
        return r[1]

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