How to create a program to calculate a polynomial in python?

Question

So this is the directions to my homework:

Write a program to calculate a polynomial. The program should ask for the user for a,b,c, and x. It should ouput the value of ax^2+ bx +c by calling a function named CalcPoly(a,b,c,x) that returns the value of the function to the main program. The main program should print, not the function.

And this is what I have so far:

def CalcPoly(a, b, c, x):

 print ("Enter the first degree: ")
 print (int(input(a)))

 print ("Enter the second degree: ")
 print (int(input(b)))

 print ("Enter the third degree: ")
 print (int(input(c)))

 print (a*x**2 + b*x + c)

CalcPoly()

And the error I got was:

Traceback (most recent call last):
 File "main.py", line 14, in <module>
  CalcPoly()
TypeError: CalcPoly() missing 4 required positional arguments: 'a', 'b', 'c', and 'x'

I don't know how to fix it and I don't even know if I did the code right. I would appreciate any assistance. Thank you so much!

Answer 1

Try this:

def CalcPoly(a, b, c, x):
    print (a*x**2 + b*x + c)

if __name__=="__main__":
    a = int(input("Enter the first degree: "))
    b = int(input("Enter the second degree: "))
    c = int(input("Enter the third degree: "))
    
    CalcPoly(a, b, c, 4) # x=4

    # Console:
    # Enter the first degree: 1
    # Enter the second degree: 2
    # Enter the third degree: 3
    # 27

Answer 2

The function CalcPoly expects the arguments of the polynomial coefficients and the value of variable x .

You can call the function correctly as follows:

CalcPoly(1,2,3,4)

This will evaluate the equation as x^2 + 2x + 3 where x=4 .

But, if you are reading inputs, you must define function as follows:

def CalcPoly()

And also, please do not forget to read input for the value of x .

Answer 3

There are a lot of things wrong in your code.

First, the reason for the error itself-

def CalcPoly(a, b, c, x):

This takes in 4 arguments, a , b , c , and x , you pass none of them when calling the function-

CalcPoly()

Now, that is far from the end of the story. In python you take input like this-

a = int(input())

This gets user input and stores it into a . I'm assuming that's what you wanted to do, any argument within the parens of input() means that will be printed as a prompt-

a = int(input("Enter the first degree: "))

This will prompt the user,

Enter the first degree:

then wait for user input, turn it into an int and store it inside a

All the other input should be the same.

Your question says you should be taking input for a , b , c , and x , not just a , b , c .

So your fixed up function should look like-

def CalcPoly(a, b, c, x):

 a = int(input("Enter the first degree: "))

 b = int(input("Enter the second degree: "))

 c = int(input("Enter the third degree: "))
 
 x = int(input("Enter the x value: "))

 print(a*x**2 + b*x + c)

This is really basic stuff, you should read the python docs tutorial

Answer 4

Since you say that the main program should print and not the function, you may try this.

def CalcPoly(a, b, c, x):
      result = (a*x**2) + (b*x) + c
      return result
a = int(input("Enter the coefficient of x^2 (a): "))
b = int(input("Enter the coefficient of x (b): "))
c = int(input("Enter the constant (c): "))
x = int(input("Enter x :"))
value = CalcPoly(a, b, c,x)
print(value)

Also you were facing an issue with your code, that is -

TypeError: CalcPoly() missing 4 required positional arguments: 'a', 'b', 'c', and 'x'

This is because while defining the CalcPoly() function you have declared 4 positional arguments a, b, c and x and while calling the function you haven't given the values of a, b, c and x in the function call.

Answer 5

I'd like to add an object-oriented approach here. Let's create a class where the method get_input collects inputs from users and the method __call__ basically performs the polynomial calculation. This way you can separate the process of data collection and the actual calculation.

from typing import Union

class CalcPoly:
    def get_input(self):
        a: int = int(input("Enter the first degree:"))
        b: int = int(input("Enter the second degree:"))
        c: int = int(input("Enter the third degree:"))
        x: Union[int, float] = input("Enter x:")
        return a, b, c, x

    def __call__(self):
        a, b, c, x = self.get_input()
        return (a*x**2) + (b*x) + c

calc = CalcPoly()
print(calc())