Learn Interfaces by Building an Equation Solver - Step 30

Python
1

Tell us what’s happening:

Still can’t find the code that passes. I think something is missing or wrong in the instructions!
What is left here?
def init(self, args):
super.init(args)
a, b, c = self.coefficients.values()
self.delta = b**2 - 4ac

Your code so far

from abc import ABC, abstractmethod

class Equation(ABC):
    degree: int
  
    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'"
            )

    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')                
        equation_string = ' '.join(terms) + ' = 0'
        return equation_string.strip('+')        
    
    @abstractmethod
    def solve(self):
        pass
        
    @abstractmethod
    def analyze(self):
        pass
        
class LinearEquation(Equation):
    degree = 1
    
    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
    def __init__(self, *args):
        super.__init__(*args)
        a, b, c = self.coefficients.values()
        self.delta = b**2 - 4*a*c


# User Editable Region

    

# User Editable Region

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

lin_eq = LinearEquation(2, 3)
print(lin_eq)

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Challenge Information:

Learn Interfaces by Building an Equation Solver - Step 30

2

What error/hint are you getting?

1 Like
3

No errors, this comment:
“// running tests
3. You should call super()._init_(*args) within your _init_ method.
4. You should declare a delta attribute within your _init_ method and assign it the value of the discriminant of the equation.
// tests completed
// console output
2x +3 = 0“
Both issues are covered, what am I missing?

4

Take a closer look at the hint, and the:

        super.__init__(*args)
1 Like