Learn Interfaces by Building an Equation Solver - Step 53

Python
1

Tell us what’s happening:

Hi, I am stuck in this piece of the code. Can anyone tell what is wrong in the code?
The hint says: The ‘solve’ function should return a different string.

Your code so far

from abc import ABC, abstractmethod
import re


class Equation(ABC):
    degree: int
    type: str
  
    def __init__(self, *args):
        if (self.degree + 1) != len(args):
            raise TypeError(
                f"'Equation' object takes {self.degree + 1} positional arguments but {len(args)} were given"
            )
        if any(not isinstance(arg, (int, float)) for arg in args):
            raise TypeError("Coefficients must be of type 'int' or 'float'")
        if args[0] == 0:
            raise ValueError("Highest degree coefficient must be different from zero")
        self.coefficients = {(len(args) - n - 1): arg for n, arg in enumerate(args)}

    def __init_subclass__(cls):
        if not hasattr(cls, "degree"):
            raise AttributeError(
                f"Cannot create '{cls.__name__}' class: missing required attribute 'degree'"
            )
        if not hasattr(cls, "type"):
            raise AttributeError(
                f"Cannot create '{cls.__name__}' class: missing required attribute 'type'"
            )

    def __str__(self):
        terms = []
        for n, coefficient in self.coefficients.items():
            if not coefficient:
                continue
            if n == 0:
                terms.append(f'{coefficient:+}')
            elif n == 1:
                terms.append(f'{coefficient:+}x')
            else:
                terms.append(f"{coefficient:+}x**{n}")
        equation_string = ' '.join(terms) + ' = 0'
        return re.sub(r"(?<!\d)1(?=x)", "", equation_string.strip("+"))        

    @abstractmethod
    def solve(self):
        pass
        
    @abstractmethod
    def analyze(self):
        pass


class LinearEquation(Equation):
    degree = 1
    type = 'Linear Equation'
    
    def solve(self):
        a, b = self.coefficients.values()
        x = -b / a
        return [x]

    def analyze(self):
        slope, intercept = self.coefficients.values()
        return {'slope': slope, 'intercept': intercept}


class QuadraticEquation(Equation):
    degree = 2
    type = 'Quadratic Equation'

    def __init__(self, *args):
        super().__init__(*args)
        a, b, c = self.coefficients.values()
        self.delta = b**2 - 4 * a * c

    def solve(self):
        if self.delta < 0:
            return []
        a, b, _ = self.coefficients.values()
        x1 = (-b + (self.delta) ** 0.5) / (2 * a)
        x2 = (-b - (self.delta) ** 0.5) / (2 * a)
        if self.delta == 0:
            return [x1]

        return [x1, x2]

    def analyze(self):
        a, b, c = self.coefficients.values()
        x = -b / (2 * a)
        y = a * x**2 + b * x + c
        if a > 0:
            concavity = 'upwards'
            min_max = 'min'
        else:
            concavity = 'downwards'
            min_max = 'max'
        return {'x': x, 'y': y, 'min_max': min_max, 'concavity': concavity}


def solver(equation):
    if not isinstance(equation, Equation):
        raise TypeError("Argument must be an Equation object")

# User Editable Region

    output_string = f'\n{equation.type:-^24}'
    output_string += f'\n\n{equation!s:-^24}\n\n'
    output_string += f'{"Solutions":-^24}\n\n'

# User Editable Region

    return output_string

lin_eq = LinearEquation(2, 3)
quadr_eq = QuadraticEquation(1, 2, 1)
print(solver(lin_eq))

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Challenge Information:

Learn Interfaces by Building an Equation Solver - Step 53

2

you changed this line

reset and try again

3

Yes, got it.
Thank you!

4

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