飘逸的python - 使用dis模块进行代码层次的性能剖析

标签：反汇编   python   性能   

于是使用dis来深入.

假设est_while.py代码如下.

#coding=utf-8
while 1:
    pass

while True:
    pass

下面是使用dis来进行剖析.

E:\>python -m dis test_while.py
  2           0 SETUP_LOOP               3 (to 6)

  3     >>    3 JUMP_ABSOLUTE            3

  5     >>    6 SETUP_LOOP              10 (to 19)
        >>    9 LOAD_NAME                0 (True)
             12 POP_JUMP_IF_FALSE       18

根据python官方文档,dis输出报告的格式如下.

The output is divided in the following columns:

1. the line number, for the first instruction of each line
2. the current instruction, indicated as -->,
3. a labelled instruction, indicated with >>,
4. the address of the instruction,
5. the operation code name,
6. operation parameters, and
7. interpretation of the parameters in parentheses.

而while True这里(第5行),由LOAD_NAME和POP_JUMP_IF_FALSE指令组成.

所以while True的时候, 每次循环都要检查True的值, 对应指令LOAD_NAME.

这就是为什么while True比while 1慢了.

飘逸的python - 使用dis模块进行代码层次的性能剖析

标签：反汇编   python   性能   

原文地址：http://blog.csdn.net/handsomekang/article/details/41479597