Optimizing function for execution speed

Question

I am new to Python and I'm trying to optimize this code for large numbers. However I'm struggling to find an optimized way. If I run it as it is, it takes almost 4 minutes. I know it has something to do with loop and the max and randint function. I tried to use random.random as I read that is quicker but I got almost the same result. Can you think of a better way so it doesn't take that long?

from random import randint
def func(iters, n):
 # Function to add max random numbers to a list.
 l = [0]
 for i in range(iters):
 r = randint(0, n)
 max_l = max(l)
 if r > max_l:
 l.append(r)
 else:
 l.append(max_l + 1)
 return l
func(100000, 50)

• quamrana: Your problem stems from max_l = max(l) which you calculate each time round. Instead you have the information for max_l at the end of each loop.

Answer 1

Yes as mentioned by @quamrana the last index of the list contains the max so just access instead of calculating it every time.

from random import randint
def func(iters, n):
#Function to add max random numbers to a list.
 l = [0]
 for i in range(iters):
 r = randint(0, n)
 max_l = l[-1]
 if r > max_l:
 l.append(r)
 else:
 l.append(max_l + 1)
 return l
func(100000, 50)

• a'r: On my system, this changed the runtime from ~50 seconds to <1 second.

Answer 2

You can try using random.choice function which is a bit faster:

from random import choice
def func(iters, n):
 # Function to add max random numbers to a list.
 l = [0]
 max_l = 0
 random_numbers = list(range(n))
 for _ in range(iters):
 r = choice(random_numbers)
 if r > max_l:
 l.append(r)
 max_l = r
 else:
 l.append(max_l + 1)
 max_l += 1
 return l
print(func(100000, 50))

And also you don't need to calculate max every time. The last value you insert is always the max_l value.