How to return a list of numbers of the power of 2?

Question

def problem(n):
myList = []
for j in range(0, n):
    number = 2 ** j
    myList.append(number)
return myList

I want this code to return the powers

Answer 1

If you want to do every step in O(1):

def gen(x):
   i = 2
   for n in range(x + 1):
       yield i
       i <<= 1

>>> list(gen(4))
[2, 4, 8, 16, 32]

PS: There's a typo in the question and if you want 4 numbers for gen(4), use range(x) instead