python basic note

偶尔用Python做点事情，用的时候隔了许久，又不太记得了，有时连基本的语法都忘掉，这里记录在一张纸上，方便查看。也涵盖比较实用的内容，方便信手捻来（我没写错吧

）
其中代码片段主要摘自前段时间写的一些Python代码。
Python Help

>>> python(“subprocess”)
帮助是很重要，linux程序员，你懂的

Python tutorial

https://docs.python.org/2/tutorial/

初学Python的人用这个好，计算机领域，不懂的google tutorial，你也懂的


Framework

1. Inherit, 要写大点的东西，面向对象不能少

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，有时连这些都不记得了

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
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