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vsiddharthverma
3,182 Pointsreturn not and while
import random start = 5 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 while start: a = random.randint(1,99) if even_odd(a): print ("{} is even".format(a)) else: print("{} is odd".format(a)) start-=1
I do not totally understand the meaning of return not num%2. num%2 means yields nothing? Also for while start: , if start = -1, while will return false? and the loop will stop?
Anybody can help answer? Thanks a lot!
import random
start = 5
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
while start:
a = random.randint(1,99)
if even_odd(a):
print ("{} is even".format(a))
else:
print("{} is odd".format(a))
start-=1
2 Answers
Steven Parker
231,007 Points
It may seem confusing to treat numbers as "true" and "false" (but it's very handy!).
The concept of "truthy" and "falsey" is that ordinary numbers can be treated as if they are "true" or "false" based on their value. Just remember that 0 is "falsey" (false), and all other numbers are "truthy" (true).
So "num % 2" is a remainder function. The remainder of dividing any even number by 2 is 0, and any odd number is 1. Putting "not" in front of it means to treat the value as a true/false, which means 1 will be "true" and 0 will be "false". But "not" also means to take the opposite, so anything that was true before (1) will now be "false", and anything that was false (0) will now be true. So the whole thing returns "true" if the number is even, and "false" if it is odd. The challenge calls this function "even_odd", but I think a better name might be "is_number_even".
And since 0 is "falsey", the while will consider start to be false when it is 0, and the loop will stop.
vsiddharthverma
3,182 PointsThank you Steve! Very helpful!