为什么功能较慢？(Why is function-less slower?)

 我已经构建了一个代码来计算数字的最大素数因子： 
 
import time
start_time = time.time()

num = 600851475143
while num % 2 == 0:
    num /= 2
if num == 1:
    i = 2
else:
    i = 3
    while num > 1:
        if num % i == 0:
            num /= i
        else:
            i += 2
print "%s \n --- %s seconds ---" % (i, time.time() - start_time)
 
 它运行在0.000769853591919秒。 在线搜索我发现了一个类似但更快的解决方案 。 我将这个想法应用到我的代码中，这就是结果： 
 
import time
start_time = time.time()

def lpf(num):
    while num % 2 == 0:
        num /= 2
    if num == 1:
        return 2
    else:
        i = 3
        while num > 1:
            if num % i == 0:
                num /= i
            else:
                i += 2
        return i        

l = lpf(600851475143)

print "%s \n --- %s seconds ---" % (l, time.time() - start_time)
 
 它运行在0.000453948974609秒。 它几乎是前一个的两倍。 我不明白逻辑：代码是相同的，但最长的代码运行得更快。 为什么？ 

I've built a code to compute the largest prime factor of a number:
 
import time
start_time = time.time()

num = 600851475143
while num % 2 == 0:
    num /= 2
if num == 1:
    i = 2
else:
    i = 3
    while num > 1:
        if num % i == 0:
            num /= i
        else:
            i += 2
print "%s \n --- %s seconds ---" % (i, time.time() - start_time)
 
It runs in 0.000769853591919 seconds. Searching online I've found a similar but faster solution. I applied the idea to my code and this is the result:
 
import time
start_time = time.time()

def lpf(num):
    while num % 2 == 0:
        num /= 2
    if num == 1:
        return 2
    else:
        i = 3
        while num > 1:
            if num % i == 0:
                num /= i
            else:
                i += 2
        return i        

l = lpf(600851475143)

print "%s \n --- %s seconds ---" % (l, time.time() - start_time)
 
It runs in 0.000453948974609 seconds. It's almost twice as fast as the previous one. I do not understand the logic: the code is identical, but yet the longest code runs faster. Why is it?

原文：https://stackoverflow.com/questions/33508812