Python简明入门教程

'''This is a multi-line string. This is the first line.
This is the second line.
"What's your name" I asked.
He said "Bond, James Bond."
'''

if guess == number:
  print 'Congratulations, you guessed it.' # New block starts here
elif guess < number:
  print 'No, it is a little higher than that' # Another block
else:
  print 'No, it is a little lower than that'

while running:
  guess = int(raw_input('Enter an integer : '))
  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 little 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

for i in range(1, 5):
  print i
else:
  print 'The for loop is over'

def sayHello():
  print 'Hello World!' # block belonging to the function
sayHello() # call the function

def printMax(a, b):
  if a > b:
    print a, 'is maximum'
  else:
    print b, 'is maximum'

def say(message, times = 1):
  print message * times

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)

import sys
print 'The command line arguments are:'
for i in sys.argv:
  print i

shoplist = ['apple', 'mango', 'carrot', 'banana']
print 'I have', len(shoplist),'items to purchase.'
print 'These items are:', # Notice the comma at end of the line
for item in shoplist:
  print item,
print '\nI also have to buy rice.'
shoplist.append('rice')
print 'My shopping list is now', shoplist
print 'I will sort my list now'
shoplist.sort()
print 'Sorted shopping list is', shoplist
print 'The first item I will buy is', shoplist[0]
olditem = shoplist[0]
del shoplist[0]
print 'I bought the', olditem
print 'My shopping list is now', shoplist

zoo = ('wolf', 'elephant', 'penguin')
print 'Number of animals in the zoo is', len(zoo)
new_zoo = ('monkey', 'dolphin', zoo)
print 'Number of animals in the new zoo is', len(new_zoo)
print 'All animals in new zoo are', new_zoo
print 'Animals brought from old zoo are', new_zoo[2]
print 'Last animal brought from old zoo is', new_zoo[2][2]

age = 22
name = 'Swaroop'
print '%s is %d years old' % (name, age)
print 'Why is %s playing with that python"htmlcode">

ab = {    'Swaroop'  : 'swaroopch@byteofpython.info',
       'Larry'   : 'larry@wall.org',
       'Matsumoto' : 'matz@ruby-lang.org',
       'Spammer'  : 'spammer@hotmail.com'
   }
print "Swaroop's address is %s" % ab['Swaroop']
# Adding a key/value pair
ab['Guido'] = 'guido@python.org'
# Deleting a key/value pair
del ab['Spammer']
print '\nThere are %d contacts in the address-book\n' % len(ab)
for name, address in ab.items():
  print 'Contact %s at %s' % (name, address)
if 'Guido' in ab: # OR ab.has_key('Guido')
  print "\nGuido's address is %s" % ab['Guido']



4、序列
列表、元组和字符串都是序列。序列的两个主要特点是索引操作符和切片操作符。




shoplist = ['apple', 'mango', 'carrot', 'banana']
# Indexing or 'Subscription' operation
print 'Item 0 is', shoplist[0]
print 'Item 1 is', shoplist[1]
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[:]



5、参考
当你创建一个对象并给它赋一个变量的时候，这个变量仅仅参考那个对象，而不是表示这个对象本身！也就是说，变量名指向你计算机中存储那个对象的内存。这被称作名称到对象的绑定。




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



6、字符串


name = 'Swaroop' # This is a string object
if name.startswith('Swa'):
  print 'Yes, the string starts with "Swa"'
if 'a' in name:
  print 'Yes, it contains the string "a"'
if name.find('war') != -1:
  print 'Yes, it contains the string "war"'
delimiter = '_*_'
mylist = ['Brazil', 'Russia', 'India', 'China']
print delimiter.join(mylist)  //用delimiter来连接mylist的字符




六、面向对象的编程
1、self
Python中的self等价于C++中的self指针和Java、C#中的this参考
2、创建类


class Person:
  pass # An empty block
p = Person()
print p




3、对象的方法


class Person:
  def sayHi(self):
    print 'Hello, how are you"htmlcode">

class Person:
  def __init__(self, name):
    self.name = name
  def sayHi(self):
    print 'Hello, my name is', self.name
p = Person('Swaroop')
p.sayHi()




5、类与对象的方法
类的变量 由一个类的所有对象（实例）共享使用。只有一个类变量的拷贝，所以当某个对象对类的变量做了改动的时候，这个改动会反映到所有其他的实例上。

对象的变量 由类的每个对象/实例拥有。因此每个对象有自己对这个域的一份拷贝，即它们不是共享的，在同一个类的不同实例中，虽然对象的变量有相同的名称，但是是互不相关的。


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 the population
    Person.population += 1




population属于Person类，因此是一个类的变量。name变量属于对象（它使用self赋值）因此是对象的变量。
6、继承


class SchoolMember:
  '''Represents any school member.'''
  def __init__(self, name, age):
    self.name = name
class Teacher(SchoolMember):
  '''Represents a teacher.'''
  def __init__(self, name, age, salary):
    SchoolMember.__init__(self, name, age)
    self.salary = salary




七、输入输出
1、文件


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 indicates EOF
    break
  print line,
  # Notice comma to avoid automatic newline added by Python
f.close() # close the file




2、存储器
持久性




import cPickle as p
#import pickle as p
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



3、控制台输入
输入字符串 nID = raw_input("Input your id plz")

输入整数 nAge = int(raw_input("input your age plz:\n"))

输入浮点型 fWeight = float(raw_input("input your weight\n"))

输入16进制数据 nHex = int(raw_input('input hex value(like 0x20):\n'),16)

输入8进制数据 nOct = int(raw_input('input oct value(like 020):\n'),8)
八、异常
1、try..except


import sys
try:
  s = raw_input('Enter something --> ')
except EOFError:
  print '\nWhy did you do an EOF on me"htmlcode">

class ShortInputException(Exception):
  '''A user-defined exception class.'''
  def __init__(self, length, atleast):
    Exception.__init__(self)
    self.length = length
    self.atleast = atleast
raise ShortInputException(len(s), 3)



3、try..finnally


import time
try:
  f = file('poem.txt')
  while True: # our usual file-reading idiom
    line = f.readline()
    if len(line) == 0:
      break
    time.sleep(2)
    print line,
finally:
  f.close()
  print 'Cleaning up...closed the file'




九、Python标准库
1、sys库
sys模块包含系统对应的功能。sys.argv列表，它包含命令行参数。
2、os库
os.name字符串指示你正在使用的平台。比如对于Windows，它是'nt'，而对于Linux/Unix用户，它是'posix'。

os.getcwd()函数得到当前工作目录，即当前Python脚本工作的目录路径。

os.getenv()和os.putenv()函数分别用来读取和设置环境变量。

os.listdir()返回指定目录下的所有文件和目录名。

os.remove()函数用来删除一个文件。

os.system()函数用来运行shell命令。

os.linesep字符串给出当前平台使用的行终止符。例如，Windows使用'\r\n'，Linux使用'\n'而Mac使用'\r'。

os.path.split()函数返回一个路径的目录名和文件名。

> os.path.split('/home/swaroop/byte/code/poem.txt')

('/home/swaroop/byte/code', 'poem.txt')

os.path.isfile()和os.path.isdir()函数分别检验给出的路径是一个文件还是目录。类似地，os.path.existe()函数用来检验给出的路径是否真地存在。
希望本文所述对大家的Python程序设计有所帮助。

            
           
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