python basic note

Python Help
>>> python(「subprocess」)
Python tutorial
https://docs.python.org/2/tutorial/
Framework
1. Inherit

import subprocess
 
class VirtualCommand():
        def __init__(self):
                self._cmdstr = None
                pass
 
        def cmdstr(self):
                return self._cmdstr
 
        def execute(self):
                return True
 
class Command(VirtualCommand):
        def __init__(self, cmdstr="echo hello"): # default value to cmdstr
                VirtualCommand.__init__(self)    # call init of parent
                self._cmdstr = cmdstr.strip()
 
        # called by Task methods, and can be inheritted
        def execute(self, stdin=None):
                cmd = self._cmdstr.split(" ")
                p = subprocess.Popen(cmd, stdin=stdin)
                p.wait()
                return True
 
if __name__ == "__main__":      #main entry
        cmd = Command("ls")
        cmd.execute()


2. Input and flow control basic

if __name__ == "__main__":      #main entry
        x = int(raw_input("Please enter an integer: "))
        if x < 0:
                print "Negative"
        elif x == 0:
                print "Zero"
        else:    
                print "More"
                 
        str = "this is a line"
        for word in str.split():
                print word
 
        for i in range(10):
                print i
 
        i = 0
        while i < 10:
                print i
                i += 1

3. file operation, string to int, 2d array usage
if __name__ == "__main__":
        m = [[0 for x in range(6)] for x in range(8)]  # initialization of 2d array
        with open("aa") as f:
                content = f.readlines()
        i = 0
        for line in content:
                la = line.split(",")
                m[cnt][0] = int(la[0])  #received
                m[cnt][1] = int(la[1])  #injected
        ... ...
                cnt += 1
 
4. input parameters, signal, dictionary
 
import sys
import signal
import time
 
class Generator:
    mod_name = 'generator'
    running = True
     
    help = """Usage: snorttf.py [parameter=value]
Parameters:
    hs        http speed(default is 1000)
    ds        dns speed(default is 10)
    ss        smtp speed(default is 10)
    server        smtp server
    """
 
    args = {
        'hs' : '1000',
        'ds'  : '10',      
        'ss' : '10',        
        "server" : "test11"
        }
 
    def __init__(self, args):
        self.get_input_param(args)           
         
    def get_input_param(self, input_args):
        arg_num = len(input_args)
        for i in range(1, arg_num):
            arg = input_args[i]
            elms = arg.split('=')
            if elms[0] == 'help':
                print self.help
                sys.exit(0)
#            print elms
            if elms[0] in self.args and len(elms) == 2:
                self.args[elms[0]] = elms[1]
            else:
                print 'input wrong argument:', arg
                print self.help
                sys.exit(0)  
                             
    def check_parameters(self):
        self.httpspeed = int(self.args['hs'])
        self.dnsspeed = int(self.args['ds'])
        self.smtpspeed = int(self.args['ss'])
        self.mailserver = self.args['server']
        pass
 
    def run_client(self):
        self.check_parameters()
        print "hs: " + str(self.httpspeed) + " ds: " + str(self.dnsspeed) + \
                " ss: " + str(self.smtpspeed) + " server: " + self.mailserver
        #TODO
        while self.running:
            #TODO
            time.sleep(1)
        print "exit"
 
if __name__ == "__main__":
        def signal_handler(signal, frame):
            Generator.running = False
 
        signal.signal(signal.SIGINT, signal_handler)
        g = Generator(sys.argv)
        g.run_client()
 
Basic
1. List
# 2d list, method len(), append()
>>> q = [2, 3]
>>> p = [1, q, 4]
>>> len(p)
3
>>> p[1]
[2, 3]
>>> p[1][0]
2
>>> p[1].append('xtra')     # See section 5.1
>>> p
[1, [2, 3, 'xtra'], 4]

# method sort()
>>> a = [66.25, 333, 333, 1, 1234.5]
>>> a.sort()
>>> a
[1, 66.25, 333, 333, 1234.5]

# As stack
>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7

#As Queue
#from collections import deque
>>> queue = deque(["Eric", "John", "Michael"])
>>> queue.append("Terry")           # Terry arrives
>>> queue.append("Graham")          # Graham arrives
>>> queue.popleft()                 # The first to arrive now leaves
'Eric'
>>> queue.popleft()                 # The second to arrive now leaves
'John'
>>> queue                           # Remaining queue in order of arrival
deque(['Michael', 'Terry', 'Graham'])

2. ssh through paramiko
    ssh = paramiko.SSHClient()
    ssh.load_system_host_keys()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy()) #WarningPolicy)
    ssh.connect(host, port, username, password)
    ssh.exec_command(self._cmdstr)

3. thread
    thread.start_new_thread(print_log, ("out", self._aout))

4. xml process
import xml.etree.ElementTree as ET

def get_config_env(path):
    tree = ET.parse(path)
    root = tree.getroot()
    for child in root:
        print child.tag, child.attrib, child.text


5. exception
Here try to execute task, if get any execption, perform term() to terminate any resources
    try:
        task.execute()
    except:
        task.term()
        raise

Here show an example of throw execption,
    try:
        raise NameError('HiThere')
    except NameError:
        print 'An exception flew by!'
        raise


Skills
1. When a script file is used, it is sometimes useful to be able to run the script and enter interactive mode afterwards. This can be done by passing -i before the script.

2. installation
yum install python-setuptools  # this install easy_install
easy_install paramiko    # this install any modules