How to compute a percentage increase/decrease multiplier in python without if statements

Question

I have a scenario in which the user enter a positive, 0, or negative value which represents a percentage increase, no change, or percentage decrease, respectively. Example: 2.5

Answer 1

You just need to use the distributive property of division:

multiplier = 1 + U/100.0

This is actually what your code does. You just separated three branches of a if that did exactly the same. Let's do some easy math step-by-step from your original code:

---

if U == 0:
   multiplier = 1
elif U > 0:
   multiplier = U/100.0 + 1
else:
   multiplier = (100 - (U * -1.0))/100.0

---

if U == 0:
   multiplier = 1 + 0                 #sum 0 for convenience
elif U > 0:
   multiplier = 1 + U/100.0           #swap order of addition
else:
   multiplier = (100 + U)) / 100.0    #multiplying by -1 is just changing the sign

---

if U == 0:
   multiplier = 1 + U/100.0    # since U is 0 in this branch, U/100.0 == 0
elif U > 0:
   multiplier = 1 + U/100.0
else:
   multiplier = 1 + U/100.0    # distributive property of division

---

Since the executed code is the same for the three branches, there's no point having a if:

multiplier = 1 + U/100.0