易截截图软件、单文件、免安装、纯绿色、仅160KB

Python modules : os, subprocess and commands

1. What’s the difference between all of the os.popen() methods?
popen2 doesn't capture standard error, popen3 does capture standard
error and gives a unique file handle for it. Finally, popen4 captures
standard error but includes it in the same file object as standard
output.
os.popen()   -> stdout
os.popen2() -> (stdin, stdout)
os.popen3() -> (stdin, stdout, stderr)
os.popen4() -> (stdin, stdout_and_stderr)
2. os.popen() vs os.system()
from what I've deciphered, the only differences between os.popen() and os.system() are
a) popen automatically starts a new process while system only does it if you include an &
b) popen hooks onto stdout and stdin.
If so, what's the use of os.system()???
a) is not true. Under Unix both start a new process.
The important difference (as I understand it) is popen lets you interact with the program by reading and writing pipes while it's running. system() is more of a batch mode thing, the program runs to completion, then you get the return status.
>??? If so, what's the use of os.system()?
If you just want to run a shell command and don't need to provide any stdin and don't care about stdout/stderr.
For example, if you just want to copy a directory tree from one place to another:
status = os.system("cp -r srcdir /some/where/else")
If you want to start a program, send it input and/or watch its output as it runs, then use popen().
os.system is a standard call to the C standard function call system().
It doesn't allow you to catch the output of the program like os.popendoes.
os.popen is piped open so that you can capture in your python scripts what the program outputs.
os.system simply calls the outside program and sends it's contents to stdout which can be
redirected to a file in your shell.
Call os.system if your python program doesn't need to capture anything from your outside program.


相关文档:

Python 练习3 定义类,类方法,实例方法

设计一个IP类:
设计1 要求:初始化时给定ip地址并判断ip地址的合法性
            类方法:判断ip地址合法性
            实例方法:将ip地址转化为10进制的表示形式及16进制的表示形式
   ......

python的灵活

项目需要,刚刚接触python。
今天看书看到a>b==c ,a,b,c为integer
在C/C++/C#中,a>b为boolean,不可与integer比较相等
但python a>b==c等效于((a>b)&&(b==c))
在python中的写法是a>b and b==c ......

Python标准库 traceback模块

Example 2-18 展示了 traceback 模块允许你在程序里打印异常的跟踪返回
(Traceback)信息, 类似未捕获异常时解释器所做的. 如 Example 2-18 所示. 2.11.0.1. Example
2-18. 使用 traceback 模块打印跟踪返回信息 File: traceback-example-1.py # note!
import
Example 2-18 展示了 traceback 模块允许你在程序里打印异常 ......

python 中 base64 压缩图片,用post传送


Including binaries in your sources
+y F J2A T&N1H f(L ]0
Sometime it's handy to include small files in your sources (icons, test files, etc.)CNOUG博客首页 P x z c W R K+x3{ N
CNOUG博客首页 h I A O$k-n P
Let's take a file (myimage.gif) and convert it in base64 (optionnaly compressing it wit ......

python 中文问题

如果Python源文件中出现中文,需要在源文件第一行加上类似如下的代码页指令:
# -*- coding:gbk -*-
如果程序的运行结果中包含中文,可以在程序开头包含如下代码,就可以正确显示中文结果:
    import sys
    reload(sys)
    sys.setdefaultencoding('gbk')
......
© 2009 ej38.com All Rights Reserved. 关于E健网联系我们 | 站点地图 | 赣ICP备09004571号