Happy numbers

What is happy number?

def digsum(num):

i=num

sum=0

while i>0:

temp=i%10

sum+=temp**2

i//=10

return sum

def isahappy(num):

i=digsum(num)

while i>1:

i=digsum(i)

if i==1:

print("%d is a happy number"%(num))

else:

print("%d is not a happy number"%(num))

i=int(input("enter a number "))

isahappy(i)