I am facing a major issues in python using sympy. I didn't find any solutions to my problem or at least, I couldn't apply the solutions I found on my problem.
import sympy as sp
import math as ma
import numpy as np
E1=72500
A1=15
U01,s,C1,U02 = sp.symbols("U01,s,C1,U02")
u1 = sp.symbols("u1", cls=sp.Function)
eqs=sp.Eq(E1*A1*u1(s).diff(s)+180+U02,0)
sol=sp.dsolve(eqs,dict=True)
expr=sol.args[1]
u1=sp.lambdify(s,expr.subs(C1,U01))
print(u1(s))
#gives me : U01 - 9.19540229885057e-7*U02*s - 0.00016551724137931*s
expression1=u1(10)-54
expression2=u1(7)-99
eq1=sp.Eq(expression1,0)
eq2=sp.Eq(expression2,0)
solution = sp.solve([eq1,eq2],[U01,U02])
U01=float(solution[U01])
U02=float(solution[U02])
print(u1(55))
# gives me : U01 - 5.05747126436782e-5*U02 - 0.00910344827586207
I want to evaluate u1(55), but I still get the expression.
Thank you very much in advance.
I expect to get :
-621.0000000000018
Don't override U01 and U02 by numerical values, use intermediate variables. You have to evaluate your lambda function with solution previously found:
...
solution = sp.solve([eq1, eq2], [U01, U02])
U01_val = float(solution[U01])
U02_val = float(solution[U02])
result = u1(55).evalf(subs={U01: U01_val, U02: U02_val})
print(result)
# Output
-621.000000000001
Or simply:
...
solution = sp.solve([eq1, eq2], [U01, U02])
result = u1(55).evalf(subs=solution)
print(result)
# Output
-621.000000000001