如何从Symphy中的NotImplementedError获取值？

Question

我正在使用以下代码：

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，我得到这个错误消息：

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），我如何从那里得到那个值？。我在documentation中找不到那个部分

Answer 1

如果Symphy找不到解析解，将发生NotImplementedError。您可以通过数值方式来解决此问题：

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

这个问题不会在初等函数方面不太可能有封闭形式，请参见https://math.stackexchange.com/questions/46934/what-is-the-solution-of-cosx-x/1174794#1174794和https://mathworld.wolfram.com/DottieNumber.html