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# Even_Odd Loop

Code Challenge:

Treehouse starter code provided:

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

First task: For this challenge, we're going to need to use the random library. Add an import to the top of your file to bring it in.

Second task: Here's another easy step. Make a new variable, outside of the even_odd function, named start that's assigned to the number 5.

Third task: Make a while loop that runs until start is falsey. Inside the loop, use random.randint(1, 99) to get a random number between 1 and 99. If that random number is even (use even_odd to find out), print "{} is even", putting the random number in the hole. Otherwise, print "{} is odd", again using the random number. Finally, decrement start by 1.

even.py
```import random

start = 5

while start:
even_odd(start)
start -= 1

def even_odd(num):
num = random.randint(1, 99)
# If % 2 is 0, the number is even.
if num % 2:
print("{} is even".format(num))
else:
# Since 0 is falsey, we have to invert it with not.
return not num % 2
print("{} is odd".format(num))

even_odd(num)
```

Firstly you dont have to write even_odd function yourself. The starter code given is sufficient to implement the functionality and no additional code is needed there.

```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
```

The above code will return opposite of expression 'num%2'.

you have to import random which will be used to get the radom-number-generator.

```import random
```

And create a variable 'start' with value 5.

```start = 5
```

finally write a while loop that loop through the non-zero value of start variable.

```while start:
#some code here.
```

Inside the loop:

• get a random number between 1 and 99 using random.randint(1,99)
• print if the number is even or odd using format function
```#random number
num = random.randint(1,99)
#checking if number is even or odd
if even_odd(num):
#printing the number as per the result.
print('{} is odd/even'.format(num))
```

Final code:

```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

import random

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
```

Hi Krishna. Thank you for your help. However I need clarification on the function itself. There was no code that carried out operation of dividing the number by 2. Or is that done by the "return not num % 2" ? I haven't studied the documentation up to that point. More clarifications please. Thank you.

in a programming language, this is something a function does... broadly.

input -> [function] -> output

Now function returns the output using 'return' keyword.

So, lets talk about the line

```return not num%2
```

everything after return is an expression(tokens+operators).

Now if there is some problem in the way these tokens(or literals) and operators are arranged we get an error(most probably a syntax error).

Wait... you know that too.

In our expression we already have identified two operators... 'not' and '%'. Lets act like a compiler and start Expression evaluation:

• i have to return 'not num % 2'
• 'not' is an operator, so i have to return toggle(opposite) of 'num%2'
• agh! num%2 is an expression, with operator %
• evaluating num%2 (for even its 0 and for odd its 1)
• toggling result from expression (for even its True[0 is false in boolean] and for odd its False[non-zero is true in boolean])
• finally return what ever we got from 'not'... (for even its True, for odd its False).

Hope it helped, if not please do mention so.