# Learn Interfaces by Building an Equation Solver - Step 57

### Tell us what’s happening:

is this now how you would do it, could someone help?

``````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:
coefficient
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}

degree = 2

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")

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

# User Editable Region

match len(results):
case 0:
result_list = ['No real roots']
case 1:
result_list = [f'x = {results[0]:+}']
case 2:
result_list=[f'x2={results[1]:+}', f'x2={results[2]:+}']

# User Editable Region

case 2:
result_list = [f'x1 = {resuts[0]:+}', f'x2 = {results[1]:+}']
return output_string

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

``````

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### Challenge Information:

Learn Interfaces by Building an Equation Solver - Step 57

I am on the case 2 code for match Len(results)

Hi @Ismail8

What do you think? Is this a valid case?

And an observation: you can have only one case per conditional expressions, where conditional expression is:

`case <conditional expression>:`

this? root1, root2 = results
result_list = [
f’x1 = {root1:+}‘, # Format root1 with a sign
f’x2 = {root2:+}’ # Format root2 with a sign
]

``````root1, root2 = results
result_list = [
f'x1 = {root1:+}',  # Format root1 with a sign
f'x2 = {root2:+}'   # Format root2 with a sign
]
``````

No bad! Unfortunately Freecodecamp tests are designed to check only specific solutions.

Try to do something similar but without unpacking the list?

(NOTE: unpacking the list would add some more code in this case, which might become unnecessary. Furhtermore, it might consume additional memory in large data projects. But again: don’t lose that example - it might be the right thing to do in many other situations!! Actually… I invite you to think where (ie. scope) the unpack should be placed on your code in a scenario where you should use it for a similar example. Which scope? Global? Function? Case? …?)