牛掰的python与unix

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python的中心哲学

Python 2.7.5 (default, Nov 6 2016, 00:28:07)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import this
The Zen of Python, by Tim PetersBeautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

IPython和Bash

IPython与Bash输出hello pyyu

[root@py_unix ~]# ipython
Python 2.7. (default, Nov , ::)
Type "copyright", "credits" or "license" for more information.IPython 3.2. -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.In []: print "hello pyyu"
hello pyyu

[root@py_unix ~]# echo "Hello pyyu"
Hello pyyu

IPython与Bash执行命令

Bash查看当前目录下的文件
[root@py_unix opt]# ls -l ./
总用量
-rw-r--r-- root root 6月 : access.log
-rw-r--r-- root root 6月 : get_ip.py
drwxr-xr-x root root 6月 : mysql
-rw-r--r-- root root 8月 mysql-5.5.-linux2.-x86_64.tar.gz
drwxr-xr-x root root 7月 : redis

In []: import subprocessIn []: subprocess.c
subprocess.call subprocess.check_call subprocess.check_output In []: subprocess.call(["ls","-l","/opt"])
总用量
-rw-r--r-- root root 6月 : access.log
-rw-r--r-- root root 6月 : get_ip.py
drwxr-xr-x root root 6月 : mysql
-rw-r--r-- root root 8月 mysql-5.5.-linux2.-x86_64.tar.gz
drwxr-xr-x root root 7月 : redis
Out[]:

Subprocess与import的过程

In [5]: subprocess.call(["some_command","some_argument","another_argument_or_path"])
---------------------------------------------------------------------------
OSError Traceback (most recent call last)
<ipython-input-5-541ed8cab1e8> in <module>()
----> 1 subprocess.call(["some_command","some_argument","another_argument_or_path"])/usr/lib64/python2.7/subprocess.pyc in call(*popenargs, **kwargs)
522 retcode = call(["ls", "-l"])
523 """
--> 524 return Popen(*popenargs, **kwargs).wait()
525
526 /usr/lib64/python2.7/subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
709 p2cread, p2cwrite,
710 c2pread, c2pwrite,
--> 711 errread, errwrite)
712 except Exception:
713 # Preserve original exception in case os.close raises./usr/lib64/python2.7/subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, to_close, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
1325 raise
1326 child_exception = pickle.loads(data)
-> 1327 raise child_exception
1328
1329 OSError: [Errno 2] No such file or directory

python脚本的运行

[root@py_unix home]# cat ls.py
#!/usr/bin/env python
#python wrapper for ther ls command
import subprocess
subprocess.call(["ls","-l"])[root@py_unix home]# python ls.py
总用量 4
-rw-r--r-- 1 root root 106 8月 20 09:17 ls.py

[root@py_unix home]# cat osinfo.py
#!/usr/bin/env python
# A System Information Gathering Script
import subprocess
#Command 1
uname = "uname"
uname_arg = "-a"
print "Gathering system information with %s command:\n" % uname
subprocess.call([uname,uname_arg])
#command 2
diskspace = "df"
diskspace_arg = "-h"
print "Gathering diskspace information %s command:\n" %diskspace
subprocess.call([diskspace,diskspace_arg])

输出结果:

[root@py_unix home]# python osinfo.py
Gathering system information with uname command:Linux py_unix 3.10.0-514.21.1.el7.x86_64 #1 SMP Thu May 25 17:04:51 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
Gathering diskspace information df command:文件系统容量已用可用已用% 挂载点
/dev/mapper/cl-root 17G 3.8G 14G 22% /
devtmpfs 478M 0 478M 0% /dev
tmpfs 489M 0 489M 0% /dev/shm
tmpfs 489M 6.8M 482M 2% /run
tmpfs 489M 0 489M 0% /sys/fs/cgroup
/dev/sda1 1014M 184M 831M 19% /boot
tmpfs 98M 0 98M 0% /run/user/0

python和bash查看内核信息和内存:

[root@py_unix home]# cat osinfo.sh
#!/usr/bin/env bash
#A system Information Gathering Script
#Command 1
UNAME="uname -a"
printf "内核信息$UNAME \n\n"
$UNAME#Command 2
DISKSPACE="df -h"
printf "内存信息$DISKSPACE \n\n"
$DISKSPACE
#############
注意Bash的空格

subprocess模块

加载subprocess模块仅仅是将可以使用的代码文件加载进来。也可以创建自己的模块或文件，拱以后重复使用，这与加载subprocess模块的方法相同。IPython shell的一个非常好的优点就是可以对模块或者文件检查，查看其内部可用的属性。

使用Tab自动完成查看subprocess中可用的属性：

In []: subprocess.
subprocess.CalledProcessError subprocess.STDOUT subprocess.errno subprocess.mswindows subprocess.signal
subprocess.MAXFD subprocess.call subprocess.fcntl subprocess.os subprocess.sys
subprocess.PIPE subprocess.check_call subprocess.gc subprocess.pickle subprocess.traceback
subprocess.Popen subprocess.check_output subprocess.list2cmdline subprocess.select subprocess.types

查看subprocess.call的信息:

In []: subprocess.call?
Signature: subprocess.call(*popenargs, **kwargs)
Docstring:
Run command with arguments. Wait for command to complete, then
return the returncode attribute.The arguments are the same as for the Popen constructor. Example:retcode = call(["ls", "-l"])
File: /usr/lib64/python2./subprocess.py
Type: function

Python的优点之一是其交互式解释器，也称为shell。shell提供了一种能快速实现灵感、检验特性的方法，以及交互式的模块界面，能够将一些需要两三行脚本才能完成的任务一次性完成。

通常我们编写代码时，会采用同时运行文本编辑器和python的方式（稍后会有介绍，这实际上运行的就是Ipython），通过交互式的使用编辑器和shell，也就是在两者之间切换来完成程序的编写。

IPython集成了交互式Python的诸多优点。IPython具有卓越的Python shell，其性能远远优于标准Python的shell。IPython同时提供了基于控制台命令环境的定制功能，可以十分轻松的将交互式Python shell包含在各种Python应用中，甚至当作shell使用

Ipython提供了两类自动完成：完成（complete）与菜单完成（menu)。两者的差别在于'完成' 尽可能扩展当前的主题词，并提供一个可能的替换列表，而“菜单完成”会扩展主题词，直接匹配可以替换列表中的一个,并且如果连续按Tab键时，每一次都会切换到下一个可能的替换。IPython的默认自动完成是‘完成’。也可以通过设置修改。