(python)abs Function Recreate Question

I'm studying how to rebuild the Python function algorithm. It's really not easy. Below is the coding that I redefined the ABS function.

def my_abs(number):
    if number < 0:   
    number * -1
    elif number > 0:
    number * 1

test1 = 1.7
test2 = -8

a=my_abs(test1)
b=my_abs(test2)

print(a,b)

What's the problem?

Please give me a map~