Question

I have a class called Polynomial, and it stores information to the polynomial in a dictionary. The keys are the exponents and the values are the coefficients. To create an instance of the Polynomial class, you type the following:

P1 = Polynomial((2, 14), (2, 11), (-12, 3), (42, 0))

The first item in the pairing is the coefficient, and the second item is the exponent.

The initialization looks like this:

class Polynomial:
def __init__(self, *termpairs):
    termdict = dict(termpairs)
    self.termdict = {}
    for x, y in termdict.items():
        self.termdict[y] = x

Now if I have two coefficients that are the same, for example ((2, 14), (2, 11)), It will only create a dictionary for one of them like so:

{11: 2}

Im not sure why the one pairing is not showing up. Any thoughts?

Answer 1

The problem is here:

termdict = dict(termpairs)

You are “converting” your termpairs to a dict, so you will get something like:

((2, 14), (2, 11), (-12, 3), (42, 0)) => {2: 14, 2: 11, -12: 3, 42: 0}

In a dict there cannot be two items with the same key, so the second one (2: 11) is overwriting the first one (2: 14).

EDIT: Why are you converting it to a dict anyway? This would be a simpler solution (with no dict conversion):

def __init__(self, *termpairs):
    self.termdict = {}
    # termpairs is a tuple of tuples
    for x, y in termdict:
        self.termdict[y] = x