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Python2.5/2.6實用教程入門基礎(chǔ)篇

更新時間：2009年11月29日 21:17:46 作者：

本文方便有經(jīng)驗的程序員進入Python世界.本文適用于python2.5/2.6版本.

起步走

 
#! /usr/bin/python 

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

知識點

Python是動態(tài)語言,變量不須預(yù)先聲明.
打印語句采用C風(fēng)格
字符串和數(shù)字
但有趣的是,在javascript里我們會理想當(dāng)然的將字符串和數(shù)字連接,因為是動態(tài)語言嘛.但在Python里有點詭異,如下:

復(fù)制代碼代碼如下:

 
#! /usr/bin/python 

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

運行這行程序會出錯,提示你字符串和數(shù)字不能連接,于是只好用內(nèi)置函數(shù)進行轉(zhuǎn)換

復(fù)制代碼代碼如下:

 
#! /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) 

知識點:

用int和str函數(shù)將字符串和數(shù)字進行轉(zhuǎn)換
打印以#開頭,而不是習(xí)慣的//
打印多個參數(shù)的方式
國際化
寫膩了英文注釋,我們要用中文!

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

print "上帝重返人間:馬拉多納出任阿根廷國家足球隊主帥."
知識點:

加上字符集即可使用中文
列表
列表類似Javascript的數(shù)組,方便易用

復(fù)制代碼代碼如下:

 

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

#定義元組 
word=['a','b','c','d','e','f','g'] 

#如何通過索引訪問元組里的元素 
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. 

#元組可以合并 
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 

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

知識點:

列表長度是動態(tài)的,可任意添加刪除元素.
用索引可以很方便訪問元素,甚至返回一個子列表
更多方法請參考Python的文檔
字典

復(fù)制代碼代碼如下:

 
#! /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] 

知識點:

將他當(dāng)Java的Map來用即可.
字符串
比起C/C++,Python處理字符串的方式實在太讓人感動了.把字符串當(dāng)列表來用吧.

復(fù)制代碼代碼如下:

 
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) 

不過要注意Asc和Unicode字符串的區(qū)別:

復(fù)制代碼代碼如下:

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

s=raw_input("輸入你的中文名,按回車繼續(xù)"); 
print "你的名字是 : " +s; 

l=len(s) 
print "你中文名字的長度是:"+str(l); 
a=unicode(s,"utf8") 
l=len(a) 
print "對不起,剛才計算錯誤.我們應(yīng)該用utf8來計算中文字符串的長度, \ 
你名字的長度應(yīng)該是:"+str(l); 

知識點:

用unicode函數(shù)進行轉(zhuǎn)碼
條件和循環(huán)語句

復(fù)制代碼代碼如下:

 
#! /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) 

知識點:

條件和循環(huán)語句
如何得到控制臺輸入
函數(shù)

復(fù)制代碼代碼如下:

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

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


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

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

一個好用的函數(shù)

復(fù)制代碼代碼如下:

 
#! /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 

知識點:

Python 不用{}來控制程序結(jié)構(gòu),他強迫你用縮進來寫程序,使代碼清晰.
定義函數(shù)方便簡單
方便好用的range函數(shù)
異常處理

復(fù)制代碼代碼如下:

 
#! /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!" 