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Python Python Basics (2015) Letter Game App Even or Odd Loop

Jonatan Spahn
Jonatan Spahn
6,362 Points
Posted by Jonatan Spahn
Jonatan Spahn
6,362 Points

Can some one explain this for me, thank you!

Hello can someone explain the code for me I get most of it, but I'm not making the complete connection. I'll go line by line, and yeah this might be silly but I don't want to proceed with out fully understanding it.

import random # so here we are importing from a library

def even_odd(num): # I get that you always get a 0 if its an even number, and that since 0 is traditional = to a false value we bring in the not. So if the num is 10 we would get 0 so we would return True? if it was if their was a remainder of 1 we would return False?

# If % 2 is 0, the number is even.
# Since 0 is falsey, we have to invert it with not.
return not num % 2

start = 5 # setting up the counter for the while loop so it can eventually turn false

while start != 0: num = random.randint(1, 99) if even_odd(num):

at this point num will be a random number that goes into the even_odd function. If its even it will return a True value, but how does it know that an even correlates to the first print? Does the script assume true until it is false? and so once it gets a false value it goes to the else section of the statement?

    print("{} is even".format(num)) 
else:
    print("{} is odd".format(num))  
start -= 1

Hopefully my rambles are a little coherent and again, thank you for the help.

even.py 
import random

def even_odd(num):
    # If % 2 is 0, the number is even.
    # Since 0 is falsey, we have to invert it with not.
    return not num % 2

start = 5

while start != 0:
    num = random.randint(1, 99)
    if even_odd(num):
        print("{} is even".format(num))  # <-- sentence period removed
    else:
        print("{} is odd".format(num))  # <-- sentence period removed
    start -= 1
gyorgyandorka
gyorgyandorka
13,811 Points

Zachary Williamson Just a technical sidenote about using the forums: instead of adding comments, I suggest posting regular answers, because they can be upvoted and marked as "answered" and others can see them when browsing through the questions (like "OK, no further help needed here").

1 Answer

Zachary Williamson
seal-mask
.a{fill-rule:evenodd;}techdegree
Zachary Williamson
Python Web Development Techdegree Student 3,347 Points
Zachary Williamson
.a{fill-rule:evenodd;}techdegree
Zachary Williamson
Python Web Development Techdegree Student 3,347 Points

I'll do my best, I think I know where your confusion lies:

def even_odd(num): # I get that you always get a 0 if its an even number, and that since 0 is traditional = to a false value we bring in the not. So if the num is 10 we would get 0 so we would return True? if it was if their was a remainder of 1 we would return False?

You've pretty much got it spot on here. As the challenge comments say, since 0 by default is False, you have to make it True.

at this point num will be a random number that goes into the even_odd function. If its even it will return a True value, but how does it know that an even correlates to the first print? Does the script assume true until it is false? and so once it gets a false value it goes to the else section of the statement?

The way loops operate, is you're basically going through each condition in order. So if your program generates a number that you know is odd (and will return false), the way the code is structured it will still check if it's even first:

    if even_odd(num): #this is the first condition, so it will test if the number is even first
        print("{} is even".format(num)
    else: #if it's not even, it moves to the next condition
        print("{} is odd".format(num))

I hope that makes sense. For each condition you have in an if loop (if, elif, elif, else), it goes through each condition in order to check if that condition is true.