# Learn Interfaces by Building an Equation Solver - Step 17

### Tell us what’s happening:

I’m trying to make a dictionary with the coefficients of the equation, but I’m stuck. Please help me!
I’ve tried this code `self.coefficients = {key: val for (key, val) in enumerate(args)}` with and without tuple notation, with `str(key)` instead of `key`, and so on.

``````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")

# User Editable Region

self.coefficients = {key: val for key, val in enumerate(args)}

# User Editable Region

def __init_subclass__(cls):
if not hasattr(cls, "degree"):
raise AttributeError(
f"Cannot create '{cls.__name__}' class: missing required attribute 'degree'"
)

@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)
``````

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### Challenge Information:

Learn Interfaces by Building an Equation Solver - Step 17

Instructions:

For example, a `LinearEquation` object instantiated with `2` and `4` should have the following `coefficients` attribute: `{1: 2, 0: 4}` , because `2` corresponds to the first degree of `x` and `4` corresponds to zero-th degree of `x` .

Let’s check what your code does:
I changed the last line to `lin_eq = LinearEquation(2, 4)` to match the description

then, I have added `print(self.coefficients)` right below your code
result: `{0: 2, 1: 4}`. Your coefficients do not match the requirements.

Thank you! Usually I know something about math, but I was a little bit blind there.
I tried with `len(args)-key` for the dictionary key, but it only works with `self.degree-key`.

for a linear equation, the degree is 1, while len(args) is 2

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