curriculum/challenges/english/blocks/learn-interfaces-by-building-an-equation-solver/663c9f31306353460da54542.md
As you can see, the + sign is missing from the output. The number sign is displayed by default only if negative. To change this behavior, you can write a colon after the expression to be evaluated within the curly braces of your f-string, and specify the option +. This will allow you to display the sign both for positive and negative numbers.
Modify the string in your two conditional clauses by adding :+ inside the curly braces after coefficient.
You should modify the string to append to the terms list within your if statement into f'{coefficient:+}'.
({ test: () => assert(runPython(`_Node(_code).find_class("Equation").find_function("__str__").find_for_loops()[0].find_ifs()[1].find_bodies()[0].is_equivalent("terms.append(f'{coefficient:+}')")`)) })
You should modify the string to insert into the terms list within your elif clause into f'{coefficient:+}x'.
({ 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')")`)) })
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}')
elif n == 1:
terms.append(f'{coefficient}x')
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)