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curriculum/challenges/english/blocks/learn-interfaces-by-building-an-equation-solver/663c981b9b06922e13a97fe9.md

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--description--

Create an elif clause for the case n == 1. Within the elif clause, create an f-string containing the coefficient directly followed by a lowercase x and append it to the terms list.

--hints--

You should create an elif clause to check if n is equal to 1.

js
({ test: () => assert(runPython(`_Node(_code).find_class("Equation").find_function("__str__").find_for_loops()[0].find_ifs()[1].find_conditions()[1].is_equivalent("n==1")`)) })

You should append f'{coefficient}x' to the terms list within your new elif clause.

js
({ test: () => assert(runPython(`_Node(_code).find_class("Equation").find_function("__str__").find_for_loops()[0].find_ifs()[1].find_bodies()[1].is_equivalent("terms.append(f'{coefficient}x')")`)) })

--seed--

--seed-contents--

py
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'"
            )
--fcc-editable-region--
    def __str__(self):
        terms = []
        for n, coefficient in self.coefficients.items():
            if not coefficient:
                continue
            if n == 0:
                terms.append(f'{coefficient}')
        equation_string = ' '.join(terms)
        return equation_string
--fcc-editable-region--
        
    
    @abstractmethod
    def solve(self):
        pass
        
    @abstractmethod
    def analyze(self):
        pass
        
class LinearEquation(Equation):
    degree = 1
    
    def solve(self):
        pass
    
    def analyze(self):
        pass
    
lin_eq = LinearEquation(2, 3)
print(lin_eq)