# Learn Interfaces by Building an Equation Solver - Step 30

### Tell us what’s happening:

Here’s what the prompt is asking for:

“Within the QuadraticEquation class, define an init method. Use super() to call the init method from the parent class. Then, define a new attribute named delta, which stores the value of the discriminant of the equation.”

I’ve tried several ways to solve it, but I’m still getting errors. Can someone check if there’s something missing or something extra?

``````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}

degree = 2

# User Editable Region

def __init__(self, *args):
super().__init__(*args)

a, b, c = self.args
self.delta = b**2-4*a*c

# 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

There’s no `self.args`. If you want to unpack the coefficients, look at what you did previously.

Thanks for pointing that out. I’ll revisit my previous steps to see how I unpacked the coefficients. I must have missed a key detail. Appreciate the help!