python happy number demo.

gistfile1.txt

def happy_num(num):
    st = set()
    while True:
        if num == 1:
            return True
        num = sum([int(i)**2 for i in str(num)])
        if num in st:
            return False
        st.add(num)
        
def fn():
    happy_num_lst = set()
    for i in range(10000):
        if happy_num(i):
            happy_num_lst.add(i)
    return happy_num_lst
    
fn()