Python 中的积分:添加不可调用的对象 [英] Integrals in Python: Add object not callable

问题描述

我正在尝试使用梯形规则求解 sin(x) 函数的泰勒近似的积分.代码看起来不错，但它一直给我以下错误:TypeError: 'Add' object is not callable"

I'm trying to solve an integral of a taylor approximation of a sin(x) function by using the trapezoid rule. The code seems fine but it keep giving me the following error: "TypeError: 'Add' object is not callable"

这是我的代码:

 import math
 import numpy
 import sympy as sy
 import numpy as np
 from sympy.functions import sin,cos
 import matplotlib.pyplot as plt
 x = sy.Symbol('x')
 f = sin(x)
 # Factorial function
     if n <= 0:
         return 1
     else:
         return n*factorial(n-1)

 taylor_series = sin(x).series(n=None)
 # Do a trapezoid integration
     xedge = numpy.linspace(a,b,N+1)
     integral = 0.0
     n = 0
     while n < N:
         integral += 0.5*(xedge[n+1] - xedge[n])*(f(xedge[n]) + f(xedge[n+1]))
         n += 1
     return integral

 N = 3
 a = 0.0
 b = 1.0

 z = sum([next(taylor_series) for i in range(N)])
 print("Taylor series:",z)
 # Trapezoid rule result 
 N = 2
 while (N <= 2):
     dd = trap(a,b,z,N)
     print ('Trapezoid rule result:', dd)
     N *= 2

回溯:

Error: Traceback (most recent call last):
  File "Question1.py", line 86, in <module>
    dd = trap(a,b,z,N)
  File "Question1.py", line 67, in trap
    integral += 0.5*(xedge[n+1] - xedge[n])*(f(xedge[n]) + f(xedge[n+1]))
TypeError: 'Add' object is not callable

推荐答案

在你的情况下 f 是一个 sympy 表达式.你不能仅仅通过调用它来评估它；你必须使用 evalf() 方法:

In your case f is a sympy expression. You cannot just evaluate it by calling it; you have to use the evalf() method:

...
integral += 0.5*(xedge[n+1] - xedge[n])*(f.evalf(xedge[n]) + f.evalf(xedge[n+1]))
...

产生输出:

Taylor series: x**5/120 - x**3/6 + x
Trapezoid rule result: 0.0079345703125*x**5 - 0.158203125*x**3 + 1.0*x

End

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