如何从 sympy 中的 NotImplementedError 获取值？

编程问答 2022-09-04

问题描述

我正在使用此代码：

from sympy.solvers import solve
from sympy import Symbol

x = Symbol('x')

function = input("Insert function: ")

def gx(function,x):
    return solve(function,x,dict=True)

print(gx(function,x))

当我写 cos(x)+x 时，我收到此错误消息：

Traceback (most recent call last):
  File "/home/raulpenate/Documents/pyhton/MetodosNumericos/Tareas/testing.py",line 11,in <module>
    print(gx(function,x))
  File "/home/raulpenate/Documents/pyhton/MetodosNumericos/Tareas/testing.py",line 9,in gx
    return solve(function,x)
  File "/home/raulpenate/.local/lib/python3.9/site-packages/sympy/solvers/solvers.py",line 1095,in solve
    solution = _solve(f[0],*symbols,**flags)
  File "/home/raulpenate/.local/lib/python3.9/site-packages/sympy/solvers/solvers.py",line 1714,in _solve
    raise NotImplementedError('\n'.join([msg,not_impl_msg % f]))
NotImplementedError: multiple generators [x,cos(x)]
No algorithms are implemented to solve equation x + cos(x)

我想从

NotImplementedError: multiple generators [x,cos(x)]

特别是 cos(x)，我怎样才能从那里获得那个值？。我在 documentation 中找不到该部分。

解决方法

NotImplementedError 如果 sympy 找不到解析解就会出现。你可以用数字来解决这个问题：

from sympy import nsolve,cos,Symbol
x = Symbol("x")
nsolve(cos(x) + x,0) # -0.739085133215161

这个问题不会就初等函数而言不太可能有封闭形式，参见https://math.stackexchange.com/questions/46934/what-is-the-solution-of-cosx-x/1174794#1174794和https://mathworld.wolfram.com/DottieNumber.html

algebraequationmathpythonsympy