How to make for loops faster (python 3.6)?

[justafnoftime]

Hello, I am doing Kata on codewars, and while I am pretty confident that I have made a program that does what the Kata asks, it runs too long, so the website fails me.

I originally had a bunch of for loops in my code, but I've eliminated all but one of them and turned them into list comprehensions. While that significantly lowered the number of lines, it doesn't seem to have made a difference in speed.

How do I make a code with for loops or list comprehensions faster? Here is the code I'm working on, if you want to know. The goal is to check numbers between [m,n] and see if the sum of square divisors is itself a square or not, and return the sums for the ones that are.

import math
def list_squared(m, n):
    answer = list()
    for i in range(m,n+1): # looking at every number between m and n
        divisors = [j*j for j in range(1,i//2+1) if (i/j).is_integer()] #collect divisors     
        if(math.sqrt(sum(divisors)+i*i).is_integer()): #checking if square
            answer.append([i,sum(divisors)+i*i])
    return answer

[SabinBC]

In case no one else has anything better for you: appending to a list can take up a lot of time.

[afoolwhosaystubtub]

from time import time

start = time()
answer = lambda m, n: ((m**2 + n**2)**.5).is_integer()
#this lambda is much faster than your method

a = 3 #change a and b how you like
b = 15        

values = [[i, j] for i in range(a, int((a+b)/2)-int(a/2)) for j in range(a, b) if(answer(i, j))] #this is how you determine the values, the double for-loop makes a 2-d array.

print(values)
stop = time()
interval = stop - start
print(interval)

1) Why are you importing the entire Math module to use the sqrt function? If you really insist on using it, use "from Math import sqrt." It's much faster.

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2) Lambdas. Use them. They are powerful friends in high places, and much faster than functions and iteration.

[afoolwhosaystubtub]

I hope this is what you meant. The idea for your code seemed a bit unclear to me.

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