Why do I get "Unorderable types: int() < str()" or "'<' not supported between instances of 'int' and 'str'" when comparing input to a number?

calculator, python

Solution

The issue here is that `input()` returns a string in Python 3.x, so when you do your comparison, you are comparing a string and an integer, which isn't well defined (what if the string is a word, how does one compare a string and a number?) - in this case Python doesn't guess, it throws an error.

To fix this, simply call `int()` to convert your string to an integer:

int(input(...))

As a note, if you want to deal with decimal numbers, you will want to use one of `float()` or `decimal.Decimal()` (depending on your accuracy and speed needs).

Note that the more pythonic way of looping over a series of numbers (as opposed to a `while` loop and counting) is to use `range()`. For example:

def main():
    print("Let me Retire Financial Calculator")
    deposit = float(input("Please input annual deposit in dollars: $"))
    rate = int(input ("Please input annual rate in percentage: %")) / 100
    time = int(input("How many years until retirement?"))
    value = 0
    for x in range(1, time+1):
        value = (value * rate) + deposit
        print("The value of your account after" + str(x) + "years will be $" + str(value))

Problem

Original source

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