On task 3 of the final part of Python basics I can't figure out what I'm doing wrong. I know its something simple.

Chris, I'm having a bit of difficulties with this one.

I can't seem to understand the logic behind the code.. I'm a bit confused by the meaning of these lines:

return not num % 2

and this section:

start = 5

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

Could you translate them for me in 'English'?

Thank you and happy new year!

Mo.

There is a little bit of wizardry going on in return not num % 2

num % 2 is modulo math that divides a number until there is only a remainder. using % 2 results in a 0 for even numbers and a 1 for odd numbers.

If looking at the "truthiness" of this result, an even number would get 0 or False, and an odd number would get 1 or True. This is the opposite of what we want.

Using a not reverses the results so not False (for even numbers) becomes True and not True (for odd numbers) becomes False.

Therefore, return not num % 2 returns True for even numbers and False for odd numbers

In the next section of code, the while loop is using the "truthiness" of start to decide to loop. As long as start isn't 0 ("falsey") then the loop continues.

# Set start to run loop 5 times
start = 5

# While start is not 0, run loop
while start:
  # Generate a random integer between 1 and 99
  num = random.randint(1,99)
  # Use even_odd function to determine if num is even (True returned) or odd (False returned)
  if even_odd(num):
      # ... Action if even
  # decrement start to count down the loops
  start -= 1

Note that the helper function even_odd() would be better named as is_even() so that the if statement makes more sense as:

  if is_even(num):
      # ... Action if even

One warning on using simple "truthiness" on a variable. If start got decremented by 2 (due to a bug) the value 0 would be missed when start jumped from 1 to -1. Negative numbers are "True" and the while loop would run forever.

Thanks for the explanation Chris!

I am getting an error that states my "code took too long to run."

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

def start():
  start = 5

while start:
  num = random.randint(1, 99)
if even_odd(num):
  print('{} is even'.format(num))
else:
  print('{} is odd'.format(num))
start -=1

Scott, your indentation is off. The last five line need indented on stop:

while start:
  num = random.randint(1, 99)
  if even_odd(num):
    print('{} is even'.format(num))
  else:
    print('{} is odd'.format(num))
  start -=1

Without the indent changes the only statement in the while loop. is the num assignment. start never changes and the loop runs forever (or until the cpu cap is hit)

Oops. Thanks Chris.