sumDigits naturals product

sumdigits_naturals_product.py

# first 10 naturals
nat = np.arange(1,10)
# multiply them
nat_df = pd.DataFrame(
    columns=nat,
    index=nat,
    data=np.matmul(nat[:,np.newaxis],nat[:,np.newaxis].T))

def sumDigits(no):
    return 0 if no == 0 else int(no % 10) + sumDigits(int(no / 10))
# sum all the digits
print(nat_df.applymap(sumDigits))

# result : 
#    1  2  3   4  5   6   7   8  9
# 1  1  2  3   4  5   6   7   8  9
# 2  2  4  6   8  1   3   5   7  9
# 3  3  6  9   3  6   9   3   6  9
# 4  4  8  3   7  2   6  10   5  9
# 5  5  1  6   2  7   3   8   4  9
# 6  6  3  9   6  3   9   6  12  9
# 7  7  5  3  10  8   6  13  11  9
# 8  8  7  6   5  4  12  11  10  9
# 9  9  9  9   9  9   9   9   9  9