#! /usr/bin/env python
# -*- coding: utf-8 -*-
import datetime

def sample_loop(n):
L = []
for i in range(n):
L.append(i)
return L

def sample_comprehension(n):
return [i for i in range(n)]

d = datetime.datetime.today()
print (":",d.strftime("%Y-%m-%d %H:%M:%S") )

sample_comprehension(50000000)
d = datetime.datetime.today()
print (":",d.strftime("%Y-%m-%d %H:%M:%S") )

sample_loop(50000000)
d = datetime.datetime.today()
print (":",d.strftime("%Y-%m-%d %H:%M:%S") )

実行結果
2010-06-27 15:19:23
2010-06-27 15:19:46
2010-06-27 15:19:46

Python3だとリスト内包表現って遅いの?