Symbolic Variable Substitution: Python

Question

I wish to find the value of the given equation by substituting the value of the symbolic variable 'x'. However, the output still contains the variable:

import math
from sympy import *

m = var ('x')
x = m
i = 1

while i <= 100:
    m = sin(m)
    i = i + 1

i = 1

while i <= 7:
    k = diff(m,x)
    i = i + 1

print(k.subs(x, 0))

Output:

cos(x)*cos(sin(x))*cos(sin(sin(x)))*cos(sin(sin(sin(x))))*cos(sin(sin(sin(sin(x)))))*cos(sin(sin(sin(sin(sin(x))))))*cos(sin(sin(sin(sin(sin(sin(x)))))))*cos(sin(sin(sin(sin(sin(sin(sin(x))))))))*cos(sin(sin(sin(sin(sin(sin(sin(sin(x)))))))))*cos(sin(sin(sin(sin(sin(sin(sin(sin(sin(x))))))))))

Thank You in advance!

you want the value of the 7th derivative of 100 chained sin functions at x=0? (actually you only get the first derivative in your second loop...). please state your problem in a clear way. — hiro protagonist, Jul 30 '18 at 07:20
You can avoid introducing a python variable `x` and simply use `k.subs('x', 0)`. — Lutz Büch, Jul 30 '18 at 07:28
Yes, I want the 7th derivative of 100 chained sine function at x=0. — Yasmeen Ahmed, Jul 30 '18 at 07:45

score 0 · Answer 1 · answered Jul 30 '18 at 07:53

0

Answering based on the title, use

k.evalf(subs={x: 0})

But I really think you should work on your code. It is not Pythonic and probably does not serve the purpose you want.

answered Jul 30 '18 at 07:53

Ta.Da

68
1
10

Symbolic Variable Substitution: Python

1 Answers1