CODEWITHSUNDEEP
python-3.x
bananagurlz
bananagurlz

Reputation: 31

Cubic Polynomial in Python

For my latest project in my coding class (python), we need to program and compute a cubic function. So something like 3x^3+2x^2+7x+1. I cannot figure out how to code in the different x powers. I know this is a very simple question, but I can't find what I am looking for on the internet and have searched. How would I write out this polynomial given the 3,2,7 & 1 values? I assume I need to use numpy but can only figure that out with a degree one polynomial.

Upvotes: 0

Views: 6098

Answers (2)

hiro protagonist
hiro protagonist

Reputation: 46849

powers can be represented with ** in python (there is also a more sophisticated pow) function:

def f(x):
    return 3*x**3 + 2*x**2 + 7*x + 1

(in python ^ is the xor operator; if you use your expression python would not complain but just not calculate what you want)

if you need to be able to do symbolic math, i suggest you install the sympy package:

from sympy import symbols

def f(x):
    return 3*x**3 + 2*x**2 + 7*x + 1

x = symbols('x')

print(f(x))            # 3*x**3 + 2*x**2 + 7*x + 1
print(f(x).subs(x, 5)) # 461

Upvotes: 2

Chiheb Nexus
Chiheb Nexus

Reputation: 9257

You can also create a custom function like this example:

def cubic(x, args):
    args_len = len(args)
    for k in args:
        yield k * x ** (args_len-1)
        args_len -=1

Demo:

user_input = [3, 2, 7, 1]
user_var_x  = 1
somme = sum(cubic(user_var_x, user_input))
print(somme)

Output:

13

Upvotes: 0

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