Sir,
Is it possible to use the value of a variable to make a subsitution ?
Example:
x = symbols("x")
c = IndexedBase("c")
eq1 = c[0] + c[1]*x+c[2]*x**2
x1 = 2
eq1.subs(x,x1)
Nothing change. How can we use the value of x1, here 2 ?
Sincerely.
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`eq1 = eq1.subs(x,x1)` – JohanC Jan 12 '22 at 13:04
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Thank you. It is the affectation that makes the transformation. It is not obvious, but now I jnow it. – Pascal KREZEL Jan 12 '22 at 14:27
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See wikipedia: ["immutable objects"](https://en.wikipedia.org/wiki/Immutable_object). Sympy gotchas: [Sympy expressions are immutable](https://docs.sympy.org/latest/gotchas.html#immutability-of-expressions) – JohanC Jan 12 '22 at 15:37