compare the value with the key in a dictionary

Question

class VariableRateLoan(Loan):
    def __init__(self, term, rateDict, face):
        super(VariableRateLoan, self).__init__(term, rateDict, face)
        self._term = float(term)
        self._face = float(face)
      
        if type(rateDict) is not dict:
            print('Please enter the rate as a dict')
        else:
            self._rateDict = rateDict

    def getRate(self, T):
        keyList = list(self._rateDict.keys())
        if T > self._term:
            print('Term entered cannot exceed the total terms of this loan!')
        for i, v in enumerate(keyList):
            if keyList[i] <= T < keyList[i+1]:
                return self._rateDict[keyList[i]]
            else:
                return self._rateDict[max(self._rateDict.keys())]

Below is my test program

def main():
    rate_dict = {0: 0.03, 5: 0.05, 11: 0.07}
    loan1 = VariableRateLoan(120, rate_dict, 100000)
    print(loan1.getRate(7))

So basically, if I enter T=7 for getRate, I should get a rate at T=5, which is 0.05, but now it returns 0.07 for me. But if I enter anything below 5, it correctly gave me a 0.03 which starts from T=0. I was unsure what was wrong with my code.

keyList[i] <= T < keyList[i+1] (Here is the logic I try to achieve, if T entering is in a range between the two keys, it will return the value by using the lower key)

One thing to notice: I don't really sort the key because every dictionary passing in starts from 0, ends at a later term.

Answer 1

May not be the most elegant one, but should be simple to read at

def getRate(self, T):
    if T > self._term:
        print("Term entered cannot exceed the total terms of this loan!")
    
    required_key = max(term for term in self._rateDict if term <= T)
    return self._rateDict[required_key]