If/else statement executing incorrectly

Question

Learning python and currently learning the bisection method of solving problem. I'm writing code that should take in a users guess from 0 to 100 and attempt to find that guess using bisection. Here's the code:

answer = raw_input('Please think of a number between 0 and 100')
#I've been using 80 as my test case 

low = 0
high = 100

guess = (low+high)/2

while guess != answer:

    if guess < answer:
        low = guess
    else:
        high = guess


    guess = (low+high)/2

What I've realized is that when my guess < answer is false the else block doesn't execute, so my high number never changes. Why is this happening? Am I overlooking something here?

plamut · Accepted Answer · 2015-09-11T23:26:10.930

4

You need to convert user input to integer (raw_input() returns a string):

answer = int(raw_input(...))

Comparison fails because you are later comparing an integer to a string (which works in Python2, but would not work in Python3):

>>> 10 < "50"
True
>>> 75 < "50"
True

edited Sep 11 '15 at 23:26

answered Sep 11 '15 at 23:24

plamut

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good job pointing out in python3 they would get a helpful error message – Joran Beasley Sep 11 '15 at 23:25
Interesting. I am actually using python 2.7, but regardless that did fix my problem. – MJ49 Sep 11 '15 at 23:32

If/else statement executing incorrectly

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