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[root@Mo ~]# python -V		#查看python的版本
Python 2.6.6

[root@Mo arvon_python]# which python	#查看python命令的安装的位置
/usr/bin/python

[root@Mo arvon_python]# echo $PATH		#查看$PATH变量，可以通过which命令查看一个命令的位置
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

	#缩进可以使用Tab、2个空格、4个空格，选择一个长期用下去

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#the script is about expression
length = float(raw_input("Enter the length:"))
breadth = float(raw_input("Enter the breadth:"))
area = length * breadth
print 'Area is', area
print 'Perimeter is', 2* (length + breadth)

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: show how to use if
#number = int(raw_input("Input a number:"))
number = 25
guess = int(input("Enter a number which you are think:"))
print guess
print number
if guess == number:
    print "Your number is right"
elif guess > 25:
    print "Your number is:", guess, "It,s too big"
elif guess < 25:
    print "You number is:", guess, "is small"

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: while
number=23
running=True
while running:
    guess=int(raw_input('Enteraninteger:'))
    if guess == number:
        print 'Congratulations, you guessed it.'
        running = False #this causes the while loop to stop
    elif guess < number:
        print 'No, it is a litte higher than that'
    else:
        print 'No, it is a little lower than that'
else:
    print 'The while loop is over.'
    #Do anything else you want to do here
print 'done'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
for i in range(1, 15, 2):
    print i
else:
    print 'THe for loop is over'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: break.py
runing = 'True'
while runing:
    s = raw_input('Enter your name:')
    if s == 'quit':
        break
    print 'Length of the string is', len(s)
print 'Done'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
runing = True
while runing:
    s = raw_input('Enter something:')
    if s == 'quit':
        break
    if len(s) < 3:
        continue
    print 'Input is of sufficient length'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
def sayHello():
    print 'Hello World！'#block belonging to the function
sayHello()#call the function

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Filename:func_param.py
def printMax(a,b):
    if a>b:
        print a, 'is max number'
    else:
        print b, 'is max number'
printMax(3,4)#directly give litter values
x = 5
y = 7
printMax(x,y)#give variables as arguments

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#!/usr/bin/python
#Filename: func_local.py
def func(x):
    print 'x is', x
    x = 2
    print 'Changed local x to', x
x = 50
func(x)
print 'x is still', x

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: func_global.py
def func():
    global x
    print 'x is', x
    x = 2
    print 'Changed local x to', x
x = 50
func()
print 'Value of x is', x

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#!/usr/bin/python
#-*- coding: utf-8
#Todo: func_default.py
def say (message, times=1):
    print message*times
say('Hello')
say('World',5)

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#!/usr/bin/python
#-*- coding: utf-8 -*-
def func(a,b = 5, c=10):
    print 'a is', a, 'and b is', b, 'and c is', c
func(3, 7)
func(25, c=24)
func(c= 50, a= 100)
###Output
[root@Mo arvon_python]# python func_key.py
a is 3 and b is 7 and c is 10
a is 25 and b is 5 and c is 24
a is 100 and b is 5 and c is 50

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: func_return.py
def maximum(x, y):
    if x>y:
        return x
    else:
        return y
print maximum(2, 3)
###Output
[root@Mo arvon_python]# python func_return.py
3

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: func_doc.py
def printMax(x, y):
    '''Prints the max num of tow numbers.
    The two values must be in tetgers.'''
    x = int(x)#convert to in tegers, if possible
    y = int(y)
    if x>y:
        print x, 'is max num'
    else:
        print y, 'is max num'
printMax(3, 5)
print printMax.__doc__
###Out put
[root@Mo arvon_python]# python func_doc.py
5 is max num
Prints the max num of tow numbers.
    The two values must be in tetgers.

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: using_sys.py
import sys  #sys是system的缩写
print 'The command line arguments are:'
for i in sys.argv:
#脚本的名称总是sys.argv列表的第一个参数
    print i
print '\n\nThe PYTHON PATH is', sys.path, '\n'
###Output
[root@Mo arvon_python]# python using_sys.py
The command line arguments are:
using_sys.py


The PYTHON PATH is ['/root/arvon_python', '/usr/lib64/python26.zip', '/usr/lib64/python2.6', '/usr/lib64/python2.6/plat-linux2', '/usr/lib64/python2.6/lib-tk', '/usr/lib64/python2.6/lib-old', '/usr/lib64/python2.6/lib-dynload', '/usr/lib64/python2.6/site-packages', '/usr/lib/python2.6/site-packages']

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#!/usr/bin/python
#-*- coding: utf-8 -*-
if __name__ == ' __main__ ':
#模块是对象，并且所有的模块都有一个内置属性 __name__。一个模块的 __name__ 的值取决于您如何应用模块。如果 import 一个模块，那么模块__name__ 的值通常为模块文件名，不带路径或者文件扩展名。但是您也可以像一个标准的程序样直接运行模块，在这 种情况下, __name__ 的值将是一个特别缺省"__main__"
    print 'This program is being run by itself'
else:
    print 'I am being imorted form another module'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: creat own module.py
def sayHi():
    print 'Hi, this is my wife pikachu.'
version = '0.1'
#End of  my module.py

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#!/usr/bin/python   #使用自己创建的模块
#-*- coding: utf-8 -*-
#Todo: use my own module
import myModule
myModule.sayHi()
print 'Version',myModule.version

### Output

[root@Mo arvon_python]# python usemyModule.py
Hi, this is my wife pikachu.
Version 0.1

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>>> import sys
>>> dir(sys)
['__displayhook__', '__doc__', '__excepthook__', '__name__', '__package__', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'flags', 'float_info', 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'hexversion', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'py3kwarning', 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions']
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'sys']
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'a', 'sys']
>>> dela
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'dela' is not defined
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'a', 'sys']
>>> del a
>>> dir ()
['__builtins__', '__doc__', '__name__', '__package__', 'sys']
###说明
#首先，我们来看一下在输入的sys模块上使用dir。我们看到它包含一个庞大的属性列表。
#接下来，我们不给dir函数传递参数而使用它——默认地，它返回当前模块的属性列表。注
#意，输入的模块同样是列表的一部分。
#为了观察dir的作用，我们定义一个新的变量a并且给它赋一个值，然后检验dir，我们观察到在
#列表中增加了以上相同的值。我们使用del语句删除当前模块中的变量/属性，这个变化再一次
#反映在dir的输出中。
#关于del的一点注释——这个语句在运行后被用来 删除 一个变量/名称。在这个例子中，del a，
#你将无法再使用变量a——它就好像从来没有存在过一样。

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: using_list.py
likelist = ['apple', 'mango', 'pikachu', 'mo']
print 'I have', len(likelist), 'Just do.'
print 'These things include:',
for eachone in likelist:
    print eachone,
print '\nI just like live with her.'
likelist.append('Arvon')
print 'My life now is include:', likelist
print 'I want sort mylist now'
likelist.sort()
print 'Have done, Now the list is:', likelist
print 'The first item now is', likelist[0]
oldlist = likelist[0]
del likelist[0]
print 'I am', oldlist
print 'My list now is:', likelist
##[root@Mo arvon_python]# python useing_list.py
I have 4 Just do.
These things include: apple mango pikachu mo
I just like live with her.
My life now is include: ['apple', 'mango', 'pikachu', 'mo', 'Arvon']
I want sort mylist now
Have done, Now the list is: ['Arvon', 'apple', 'mango', 'mo', 'pikachu']
The first item now is Arvon
I am Arvon
My list now is: ['apple', 'mango', 'mo', 'pikachu']

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#!/usr/bin/python
#-*- coding: utf-8 -*-
home = ('Mo', 'Arvon', 'Pikachu')
print 'Numble of home is', len(home)
ourhome = ('Mo', 'Arvon', 'SmallArvon')
print 'Number of ourhome is', len(ourhome)
print 'All member in ourhome are', ourhome
print 'come here in later', ourhome[2]
print 'Last member is', ourhome[2][2]
### Output
root@Mo arvon_python]# python using_tuple.py
Numble of home is 3
Number of ourhome is 3
All member in ourhome are ('Mo', 'Arvon', 'SmallArvon')
come here in later SmallArvon
Last member is a

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: print_tuple.py
age = 23
name = 'Arvon'
print '%s is %d years lold' % (name, age)
#print语句可以使用跟着%符号的项目元组的字符串。这些字符串具备定制的功能。定制让输出
#满足某种特定的格式。定制可以是%s表示字符串或%d表示整数。元组必须按照相同的顺序来
#对应这些定制。
print 'Why is %s playing with that python?' % name

###Output
[root@Mo arvon_python]# python print_tuple.py
Arvon is 23 years lold
Why is Arvon playing with that python?

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: script's name is using_dict.py
ad = {'arvon':'126@126.com',
    'Mo':'Mo@mo.com',
    'Pikachu':'pikachu@love.com',
    'marry':'love@you.com'
    }
print "Arvon's email is %s" % ad['arvon']
#Adding a key/value pair
ad['life'] = 'travl@world.com'
#Deleting a key/value pair
del ad['marry']
print '\n There are %d contacts in the address-book\n' % len(ad)
for name,address in ad.items():
    print 'Contact %s at %s' % (name, address)
if 'life' in ad:
   print "\n life's address is %s" % ad['life']

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[root@Mo arvon_python]# python using_dict.py
Arvon's email is 126@126.com

 There are 4 contacts in the address-book

Contact Mo at Mo@mo.com
Contact arvon at 126@126.com
Contact life at travl@world.com
Contact Pikachu at pikachu@love.com

 life's address is travl@world.com

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: The script's name is seq.py
#
shoplist = ['apple', 'mango', 'carrot', 'banana']
#
print 'Item 0 is', shoplist[0]
print 'Item 1 is', shoplist[1]
print 'Item 2 is', shoplist[2]
print 'Item 3 is', shoplist[3]
print 'Item -1 is', shoplist[-1]
print 'Item -2 is', shoplist[-2]
# Slicing on a list
print 'Item 1 to 3 is', shoplist[1:3]
print 'Item 2 to end is', shoplist[2:]
print 'Item 1 to -1 is', shoplist[1:-1]
print 'Item start to end is', shoplist[:]
# Slicing on a string
name = 'swaroop'
print 'characters 1 to 3 is', name[1:3]
print 'characters 2 to end is', name[2:]
print 'characters 1 to -1 is', name[1:-1]
print 'characters start to end is', name[:]

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[root@Mo arvon_python]# python seq.py
Item 0 is apple
Item 1 is mango
Item 2 is carrot
Item 3 is banana
Item -1 is banana
Item -2 is carrot
Item 1 to 3 is ['mango', 'carrot']
Item 2 to end is ['carrot', 'banana']
Item 1 to -1 is ['mango', 'carrot']
Item start to end is ['apple', 'mango', 'carrot', 'banana']
characters 1 to 3 is wa
characters 2 to end is aroop
characters 1 to -1 is waroo
characters start to end is swaroop

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: refernce.py
print 'Simple Assignment'
shoplist = ['apple', 'mango', 'carrot', 'banana']
mylist = shoplist # mylist is just another name pointing to the same object!
del shoplist[0]
print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that both shoplist and mylist both print the same list without
# the 'apple' confirming that they point to the same object
print 'Copy by making a full slice'
mylist = shoplist[:] # make a copy by doing a full slice
del mylist[0] # remove first item
print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that now the two lists are different

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[root@Mo arvon_python]# python referen.py
Simple Assignment
shoplist is ['mango', 'carrot', 'banana']
mylist is ['mango', 'carrot', 'banana']
Copy by making a full slice
shoplist is ['mango', 'carrot', 'banana']
mylist is ['carrot', 'banana']

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: backup_verl.py
import os
import time
# 1. The files and directories to be backed up are specified in a list.
#source = ['/home/swaroop/byte', '/home/swaroop/bin']
source = [ '/etc']
# If you are using Windows, use source = [r'C:\Documents', r'D:\Work'] or something like that
# 2. The backup must be stored in a main backup directory
target_dir = '/mnt/e/backup/' # Remember to change this to what you will be using
# 3. The files are backed up into a zip file.
# 4. The name of the zip archive is the current date and time
target = target_dir + time.strftime('%Y%m%d%H%M%S') + '.zip'
# 5. We use the zip command (in Unix/Linux) to put the files in a zip archive
zip_command = "zip -qr '%s' %s" % (target, ' '.join(source))
# Run the backup
if os.system(zip_command) == 0:
 print 'Successful backup to', target
else:
 print 'Backup FAILED'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: backup_ver2.py
import os
import time
#1.The files and directoryes to be backed up are specified in a list.
source = ['/etc/fstab', 'etc']
#if you are using Windows, use source = [r'C:\Documents',r'D:\work']
#2.The backup must be stored in a main backup directory
target_dir = '/mnt/'
#3.The files are backed up into a zip file.
#4.The current_dir + time.strftime('%Y%m%d')
today = target_dir + time.strftime('%Y%m%d')
#The current time is the name of the zip archive
now = time.strftime('%H%M%S')
#Create the subdirectory if it isn't already threre
if not os.path.exists(today):
    os.mkdir(today)
    print 'Successfully creatd directory', today
#The name of the zip file
target = today + os.sep + now + '.zip'
#5.We use the zip command(in Unix/Linux) to put the files in a zip archive
zip_command = "zip -qr '%s' %s" % (target, ' '.join(source))
#Run the backup
if os.system(zip_command) == 0:
    print 'Successful backup to', target
else:
    print 'Backup FAILED'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: backup_ver3.py
import os
import time
#1.The files and directories to be backed up are specified in a list.
source = ['/etc/', '/etc/fstab']
target_dir = '/mnt/'
today = target_dir + time.strftime('%Y%m%d')
now = time.strftime('%H%M%S')
comment = raw_input("Enter a commnet-->")
if len(comment) == 0:#check if a comment was entered
    target = today + os.sep + now + '.zip'
else:
    target = today + os.sep + now + '_' +\
    comment.replace(' ', ' ') + '.zip'
if not os.path.exists(today):
    os.mkdir(today)
    print 'Successfully created directory', today
zip_command = "zip -qr '%s' %s" % (target, ' '.join(source))
if os.system(zip_command) == 0:
    print "Successfule backup to", target
else:
    print 'Backup FAILED'

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: simplest_class.py
class Person:
    pass#Anempty block
p = Person()
print p

#**输出：**
[root@Mo arvon_python]# python simplestclass.py
<__main__.Person instance at 0x7fdec3490d88>

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: method.py
class Person:
    def sayHi(self):
        print 'Hello, how are you?'
p = Person()
p.sayHi()
#This short example can also be written as Person().sayHi()

###Output
[root@Mo arvon_python]# python method.py
Hello, how are you?

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: class_init.py
class Person:
    def __init__(self, name):
        self.name = name
    def sayHi(self):
        print 'Hello, my name is', self.name
p = Person('Arvon')
p.sayHi()
#This short example can also be written as Person('Arvon').sayHi()

###Output
[root@Mo arvon_python]# python class_init.py
Hello, my name is Arvon

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: obj_var.py
class Person:
    '''Represents a person.'''
    population = 0
    def __init__(self, name):
        '''INitializes the person's data.'''
        self.name = name
        print '(Initializing %s)' % self.name
        #When this person is created, he/she
        #adds to population
        Person.population += 1
    def __del__(self):
        '''I am dying.'''
        print '%s says bye.'% self.name
        Person.population == 1
        if Person.population == 0:
            print 'I am the lase one.'
        else:
            print 'These are still %d people left.'% Person.population
    def sayHi(self):
        '''Greeting by the person.

           Really, that's all it does.'''
        print 'Hi, my name is %s.'% self.name
    def howMany(self):
        '''Prints the curent population.'''
        if Person.population == 1:
            print 'I am the only person here.'
        else:
            print "We have %d persons here."% Person.population
swaroop = Person('Arvon')
swaroop.sayHi()
swaroop.howMany()

###Output
[root@Mo arvon_python]# python obj_var.py
(Initializing Arvon)
Hi, my name is Arvon.
I am the only person here.
Arvon says bye.
These are still 1 people left.

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: inherit.py
class SchooMember:
    '''Represents any school member.'''
    def __init__(self, name, age):
        self.name = name
        self.age = age
        print '(Initialized SchooMember: %s)'% self.name
    def tell(self):
        '''Tell my details.'''
        print 'Name: "%s" Age: "%s"'% (self.name, self.age)
class Teacher(SchooMember):
    '''Represents a teacher.'''
    def __init__(self, name, age, salary):
        SchooMember.__init__(self, name, age)
        self.salary = salary
        print '(Initialized Teacher: %s)'% self.name
    def tell(self):
        SchooMember.tell(self)
        print 'Salary: "%d"'% self.salary
class Student(SchooMember):
    '''Represents a student.'''
    def __init__(self, name, age, marks):
        SchooMember.__init__(self, name, age)
        self.marks = marks
        print '(Initialized Student: %s)'% self.name
    def tell(self):
        SchooMember.tell(self)
        print 'Marks: "%d"'% self.marks
t = Teacher('Mo', 23, 5201314)
s = Student('Arvon', 24, 75)
print#prints a blank line
members = [t, s]
for member in members:
    member.tell()#works for both Teachers and Students

###Output
[root@Mo arvon_python]# python inherit.py
(Initialized SchooMember: Mo)
(Initialized Teacher: Mo)
(Initialized SchooMember: Arvon)
(Initialized Student: Arvon)

Name: "Mo" Age: "23"
Salary: "5201314"
Name: "Arvon" Age: "24"
Marks: "75"

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#!/usr/bin/python
#-*- coding: utf-8 -*-
poem = '''\
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!
'''
f = file('poem.txt', 'w')#open for 'w'riting
f.write(poem)#write text to file
f.close()#close the file
f = file('poem.txt')
#if no mode is specified, 'r'ead mode is assumed by default
while True:
    line = f.readline()
    if len(line) == 0:#Zero length indicatesEOF
        break
    print line,
    #Notice comma to avoid automatice new line added by Python
f.close()#close the file

###Output
[root@Mo arvon_python]# !p
python using_file.py
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: pickling.py
import cPickle as p
#import pickleasp
shoplistfile = 'shoplist.data'
#the name of the file where we will store the object
shoplist = ['apple', 'mango', 'carrot']
#Write to the file
f = file(shoplistfile, 'w')
p.dump(shoplist, f)#dump the object to a file
f.close()
del shoplist#remove the shoplist
#Read back from the storage
f = file(shoplistfile)
storedlist = p.load(f)
print storedlist

###Output
[root@Mo arvon_python]# python pickling.py
['apple', 'mango', 'carrot']

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: try_except.py
import sys
try:
    s = raw_input("Entersomething -->")
except EOFError:
    print '\nWhy did you do an EOF on me?'
    sys.exit()#exit the program
except:
    print '\nSome error/exception occurred.'
    #here, we are not exiting the program
print 'Done'

###Output
[root@Mo arvon_python]# python try_except.py
Entersomething -->hello
Done
[root@Mo arvon_python]# python try_except.py
Entersomething -->
Why did you do an EOF on me?

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#!/usr/bin/python
#-*- coding: utf-8 -*-
class ShortINputException(Exception):
    '''A user defined exception class.'''
    def __init__(self, length, atleast):
        Exception.__init__(self)
        self.length = length
        self.atleast = atleast
try:
    s = raw_input('Enter something -->')
    if len(s) < 3:
        raise ShortINputException(len(s), 3)
    #Other work can continue as usual here
except EOFError:
    print '\nWhy did you do an EOF on me?'
except ShortINputException, x:
    print 'ShortINputException: The Input was of length %d,\
        was expecting at least %d' % (x.length, x.atleast)
else:
    print 'No exception was raised.'

###Output
[root@Mo arvon_python]# python raising.py
Enter something -->
Why did you do an EOF on me?
[root@Mo arvon_python]# python raising.py
Enter something -->a
ShortINputException: The Input was of length 1,        was expecting at least 3
[root@Mo arvon_python]# python raising.py
Enter something -->abc
No exception was raised.

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: finally.py
import time
try:
    f = file('poem.txt')
    while True:#our usual file-reading idiom(成语、习语、土话)
        line = f.readline()
        if len(line) == 0:
            break
        time.sleep(2)
        print line,
finally:
    f.close()
    print 'Cleaning up... closed the file'

###Output
[root@Mo arvon_python]# python finally.py
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!
Cleaning up... closed the file

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#!/usr/bin/python
#-*- coding: utf-8 -*-
#Todo: cat.py
import sys
def readfile(filename):
    '''Print a file to the standard output'''
    f = file(filename)
    while True:
        line = f.readline()
        if len(line) == 0:
            break
        print line,#notice commma
    f.close()
#Script starts from here
if len(sys.argv) < 2:
    print 'No action specified.'
    sys.exit()
if sys.argv[1].startswith('--'):
    option = sys.argv[1][2:]
    #fetch sys.argv[1] but without the first two characters
    if option == 'version':
        print 'Version 1.2'
    elif option == 'help':
        print '''\
This program prints files to the standard output.
Any number of files can be specified.
Options include:
 --version : Prints the version number
 --help : Display this help'''
    else:
        print 'Unknown option.'
    sys.exit()
else:
    for filename in sys.argv[1:]:
        readfile(filename)

###Output
[root@Mo arvon_python]# python cat.py --help
This program prints files to the standard output.
Any number of files can be specified.
Options include:
 --version : Prints the version number
 --help : Display this help
[root@Mo arvon_python]# python cat.py --version
Version 1.2
[root@Mo arvon_python]# python cat.py --love
Unknown option.
[root@Mo arvon_python]# python cat.py poem.txt
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!