Sympy 解决返回`NoneType 对象不可编写脚本`

如何解决Sympy 解决返回`NoneType 对象不可编写脚本`

我已经用 sympy==1.7.1 和 sympy==1.5.1 对此进行了测试，并得到了相同的结果。

from sympy import *
import inspect

THT,HT,DBH,dib,c0,c1,c2,c3,c4  = symbols('THT HT DBH dib c0 c1 c2 c3 c4')
init_printing()

f = c2 + (c3*DBH) + (c4 * THT)
rhs = 1 - (((HT-1)/(THT - 1))**c1)* (1- exp(c0/f))

eqn = solve( dib - (DBH * (c0 - (f * ln(rhs)))),HT)

哪个返回

# Out [37]: 
# output

TypeErrorTraceback (most recent call last)
<ipython-input-37-619e8281e2ae> in <module>
      9 # original rhs = 1 - (((HT-1)/(THT - 1))**c1)* (1- exp(c0/f))
     10 
---> 11 eqn = solve( dib - (DBH * (c0 - (f * ln(rhs)))),HT)
     12 
     13 #eqn = solve( dib - (DBH * (b1+b2 * ln(1-(lam*p)))),HT)

~/.pyenv/versions/3.7.0/lib/python3.7/site-packages/sympy/solvers/solvers.py in solve(f,*symbols,**flags)
   1095         ok = False
   1096         if fi.has(*symset):
-> 1097             ok = True
   1098         else:
   1099             if fi.is_number:

~/.pyenv/versions/3.7.0/lib/python3.7/site-packages/sympy/solvers/solvers.py in _solve(f,**flags)
   1458         result = list(result)
   1459         if check:
-> 1460             # all solutions have been checked but Now we must
   1461             # check that the solutions do not set denominators
   1462             # in any factor to zero

TypeError: 'nonetype' object is not subscriptable
:end:

我可以解决以下配对版本：

In [47]: solve( f * ln(rhs),HT)
Out[47]: 
⎡c1___       c1___    ⎤
⎣╲╱ 0 ⋅THT - ╲╱ 0  + 1⎦

并添加一个整数代替 c0 它将解决：

solve( 2-(f * ln(rhs)),HT)

但是添加符号会导致 nonetype 错误。任何建议将不胜感激。