Python2.5/2.6实用教程入门基础篇

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概述

起步走

复制代码代码如下:

 
#! /usr/bin/python 

a=2 
b=3 
c="test" 
c=a+b 
print "execution result: %i"%c 

知识点

Python是动态语言,变量不须预先声明.
打印语句采用C风格
字符串和数字
但有趣的是,在javascript里我们会理想当然的将字符串和数字连接,因为是动态语言嘛.但在Python里有点诡异,如下:

复制代码代码如下:

 
#! /usr/bin/python 

a=2 
b="test" 
c=a+b 

运行这行程序会出错,提示你字符串和数字不能连接,于是只好用内置函数进行转换

复制代码代码如下:

 
#! /usr/bin/python 

a=2 
b="test" 
c=str(a)+b 
d="1111" 
e=a+int(d) 
#How to print multiply values 
print "c is %s,e is %i" % (c,e) 

知识点:

用int和str函数将字符串和数字进行转换
打印以#开头,而不是习惯的//
打印多个参数的方式
国际化
写腻了英文注释,我们要用中文!

#! /usr/bin/python
# -*- coding: utf8 -*-

print "上帝重返人间:马拉多纳出任阿根廷国家足球队主帅."
知识点:

加上字符集即可使用中文
列表
列表类似Javascript的数组,方便易用

复制代码代码如下:

 

#! /usr/bin/python 
# -*- coding: utf8 -*- 

#定义元组 
word=['a','b','c','d','e','f','g'] 

#如何通过索引访问元组里的元素 
a=word[2] 
print "a is: "+a 
b=word[1:3] 
print "b is: " 
print b # index 1 and 2 elements of word. 
c=word[:2] 
print "c is: " 
print c # index 0 and 1 elements of word. 
d=word[0:] 
print "d is: " 
print d # All elements of word. 

#元组可以合并 
e=word[:2]+word[2:] 
print "e is: " 
print e # All elements of word. 
f=word[-1] 
print "f is: " 
print f # The last elements of word. 
g=word[-4:-2] 
print "g is: " 
print g # index 3 and 4 elements of word. 
h=word[-2:] 
print "h is: " 
print h # The last two elements. 
i=word[:-2] 
print "i is: " 
print i # Everything except the last two characters 
l=len(word) 
print "Length of word is: "+ str(l) 
print "Adds new element" 
word.append('h') 
print word 

#删除元素 
del word[0] 
print word 
del word[1:3] 
print word 

知识点:

列表长度是动态的,可任意添加删除元素.
用索引可以很方便访问元素,甚至返回一个子列表
更多方法请参考Python的文档
字典

复制代码代码如下:

 
#! /usr/bin/python 

x={'a':'aaa','b':'bbb','c':12} 
print x['a'] 
print x['b'] 
print x['c'] 

for key in x: 
print "Key is %s and value is %s",(key,x[key]) 

keys=x.items(); 
print keys[0] 
keys[0]='ddd' 
print keys[0] 

知识点:

将他当Java的Map来用即可.
字符串
比起C/C++,Python处理字符串的方式实在太让人感动了.把字符串当列表来用吧.

复制代码代码如下:

 
word="abcdefg" 
a=word[2] 
print "a is: "+a 
b=word[1:3] 
print "b is: "+b # index 1 and 2 elements of word. 
c=word[:2] 
print "c is: "+c # index 0 and 1 elements of word. 
d=word[0:] 
print "d is: "+d # All elements of word. 
e=word[:2]+word[2:] 
print "e is: "+e # All elements of word. 
f=word[-1] 
print "f is: "+f # The last elements of word. 
g=word[-4:-2] 
print "g is: "+g # index 3 and 4 elements of word. 
h=word[-2:] 
print "h is: "+h # The last two elements. 
i=word[:-2] 
print "i is: "+i # Everything except the last two characters 
l=len(word) 
print "Length of word is: "+ str(l) 

不过要注意Asc和Unicode字符串的区别:

复制代码代码如下:

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

s=raw_input("输入你的中文名,按回车继续"); 
print "你的名字是 : " +s; 

l=len(s) 
print "你中文名字的长度是:"+str(l); 
a=unicode(s,"utf8") 
l=len(a) 
print "对不起,刚才计算错误.我们应该用utf8来计算中文字符串的长度, \ 
你名字的长度应该是:"+str(l); 

知识点:

用unicode函数进行转码
条件和循环语句

复制代码代码如下:

 
#! /usr/bin/python 
x=int(raw_input("Please enter an integer:")) 
if x<0: 
x=0 
print "Negative changed to zero" 

elif x==0: 
print "Zero" 

else: 
print "More" 


# Loops List 
a = ['cat', 'window', 'defenestrate'] 
for x in a: 
print x, len(x) 

知识点:

条件和循环语句
如何得到控制台输入
函数

复制代码代码如下:

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

def sum(a,b): 
return a+b 


func = sum 
r = func(5,6) 
print r 

# 提供默认值 
def add(a,b=2): 
return a+b 
r=add(1) 
print r 
r=add(1,5) 
print r 

一个好用的函数

复制代码代码如下:

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

# The range() function 
a =range(5,10) 
print a 
a = range(-2,-7) 
print a 
a = range(-7,-2) 
print a 
a = range(-2,-11,-3) # The 3rd parameter stands for step 
print a 

知识点:

Python 不用{}来控制程序结构,他强迫你用缩进来写程序,使代码清晰.
定义函数方便简单
方便好用的range函数
异常处理

复制代码代码如下:

 
#! /usr/bin/python 
s=raw_input("Input your age:") 
if s =="": 
raise Exception("Input must no be empty.") 

try: 
i=int(s) 
except ValueError: 
print "Could not convert data to an integer." 
except: 
print "Unknown exception!" 
else: # It is useful for code that must be executed if the try clause does not raise an exception 
print "You are %d" % i," years old" 
finally: # Clean up action 
print "Goodbye!" 