假設(shè)我們有這么一項(xiàng)任務(wù):簡(jiǎn)單測(cè)試局域網(wǎng)中的電腦是否連通.這些電腦的ip范圍從192.168.0.101到192.168.0.200.
思路:用shell編程.(Linux通常是bash而Windows是批處理腳本).例如,在Windows上用ping ip 的命令依次測(cè)試各個(gè)機(jī)器并得到控制臺(tái)輸出.由于ping通的時(shí)候控制臺(tái)文本通常是"Reply from … " 而不通的時(shí)候文本是"time out … " ,所以,在結(jié)果中進(jìn)行字符串查找,即可知道該機(jī)器是否連通.
實(shí)現(xiàn):Java代碼如下:
String cmd="cmd.exe ping "; String ipprefix="192.168.10."; int begin=101; int end=200; Process p=null; for(int i=begin;iend;i++){ p= Runtime.getRuntime().exec(cmd+i); String line = null; BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream())); while((line = reader.readLine()) != null) { //Handling line , may logs it. } reader.close(); p.destroy(); }
這段代碼運(yùn)行得很好,問(wèn)題是為了運(yùn)行這段代碼,你還需要做一些額外的工作.這些額外的工作包括:
當(dāng)然,用C/C++同樣能完成這項(xiàng)工作.但C/C++不是跨平臺(tái)語(yǔ)言.在這個(gè)足夠簡(jiǎn)單的例子中也許看不出C/C++和Java實(shí)現(xiàn)的區(qū)別,但在一些更為復(fù)雜的場(chǎng)景,比如要將連通與否的信息記錄到網(wǎng)絡(luò)數(shù)據(jù)庫(kù).由于Linux和Windows的網(wǎng)絡(luò)接口實(shí)現(xiàn)方式不同,你不得不寫(xiě)兩個(gè)函數(shù)的版本.用Java就沒(méi)有這樣的顧慮.
同樣的工作用Python實(shí)現(xiàn)如下:
import subprocess cmd="cmd.exe" begin=101 end=200 while beginend: p=subprocess.Popen(cmd,shell=True,stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE) p.stdin.write("ping 192.168.1."+str(begin)+"\n") p.stdin.close() p.wait() print "execution result: %s"%p.stdout.read()
對(duì)比Java,Python的實(shí)現(xiàn)更為簡(jiǎn)潔,你編寫(xiě)的時(shí)間更快.你不需要寫(xiě)main函數(shù),并且這個(gè)程序保存之后可以直接運(yùn)行.另外,和Java一樣,Python也是跨平臺(tái)的.
有經(jīng)驗(yàn)的C/Java程序員可能會(huì)爭(zhēng)論說(shuō)用C/Java寫(xiě)會(huì)比Python寫(xiě)得快.這個(gè)觀點(diǎn)見(jiàn)仁見(jiàn)智.我的想法是當(dāng)你同時(shí)掌握J(rèn)ava和Python之后,你會(huì)發(fā)現(xiàn)用Python寫(xiě)這類程序的速度會(huì)比Java快上許多.例如操作本地文件時(shí)你僅需要一行代碼而不需要Java的許多流包裝類.各種語(yǔ)言有其天然的適合的應(yīng)用范圍.用Python處理一些簡(jiǎn)短程序類似與操作系統(tǒng)的交互編程工作最省時(shí)省力.
足夠簡(jiǎn)單的任務(wù),例如一些shell編程.如果你喜歡用Python設(shè)計(jì)大型商業(yè)網(wǎng)站或者設(shè)計(jì)復(fù)雜的游戲,悉聽(tīng)尊便.
安裝完P(guān)ython之后(我本機(jī)的版本是2.5.4),打開(kāi)IDLE(Python GUI) , 該程序是Python語(yǔ)言解釋器,你寫(xiě)的語(yǔ)句能夠立即運(yùn)行.我們寫(xiě)下一句著名的程序語(yǔ)句:
print "Hello,world!"
并按回車.你就能看到這句被KR引入到程序世界的名言.
在解釋器中選擇"File"–“New Window” 或快捷鍵 Ctrl+N , 打開(kāi)一個(gè)新的編輯器.寫(xiě)下如下語(yǔ)句:
print "Hello,world!" raw_input("Press enter key to close this window! ");
保存為a.py文件.按F5,你就可以看到程序的運(yùn)行結(jié)果了.這是Python的第二種運(yùn)行方式.
找到你保存的a.py文件,雙擊.也可以看到程序結(jié)果.Python的程序能夠直接運(yùn)行,對(duì)比Java,這是一個(gè)優(yōu)勢(shì).
我們換一種方式來(lái)問(wèn)候世界.新建一個(gè)編輯器并寫(xiě)如下代碼:
print "歡迎來(lái)到奧運(yùn)中國(guó)!" raw_input("Press enter key to close this window!");
在你保存代碼的時(shí)候,Python會(huì)提示你是否改變文件的字符集,結(jié)果如下:
# -*- coding: cp936 -*- print "歡迎來(lái)到奧運(yùn)中國(guó)!" raw_input("Press enter key to close this window! ");
將該字符集改為我們更熟悉的形式:
# -*- coding: GBK -*- print "歡迎來(lái)到奧運(yùn)中國(guó)!" # 使用中文的例子 raw_input("Press enter key to close this window");
程序一樣運(yùn)行良好.
用微軟附帶的計(jì)算器來(lái)計(jì)數(shù)實(shí)在太麻煩了.打開(kāi)Python解釋器,直接進(jìn)行計(jì)算:
a=100.0 b=201.1 c=2343 print (a+b+c)/c
可以如下打印出預(yù)定義輸出格式的字符串:
print """ Usage: thingy [OPTIONS] -h Display this usage message -H hostname Hostname to connect to """
字符串是怎么訪問(wèn)的?請(qǐng)看這個(gè)例子:
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)
請(qǐng)注意ASCII和UNICODE字符串的區(qū)別:
print "Input your Chinese name:" s=raw_input("Press enter to be continued "); print "Your name is : " +s; l=len(s) print "Length of your Chinese name in asc codes is:"+str(l); a=unicode(s,"GBK") l=len(a) print "I'm sorry we should use unicode char!Characters number of your Chinese \ name in unicode is:"+str(l);
類似Java里的List,這是一種方便易用的數(shù)據(jù)類型:
word=['a','b','c','d','e','f','g'] a=word[2] print "a is: "+a b=word[1:3] print "b is: " print b # index1 and 2 elements of word. c=word[:2] print "c is: " print c # index0 and 1 elements of word. d=word[0:] print "d is: " print d # All elements of word. 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 # index3 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[圖片上傳中...(image-b4ced-1616074265420-0)] " word.append('h') print word
# Multi-way decision x=int(raw_input("Please enter an integer:")) if x0: x=0 print"Negative changed to zero" elif x==0: print "Zero" else: print "More" # Loops List a= ['cat', 'window', 'defenestrate'] for x ina: print x, len(x)
# Define and invoke function. def sum(a,b): return a+b func = sum r = func(5,6) print r # Defines function with default argument def add(a,b=2): return a+b r=add(1) print r r=add(1,5) print r
并且,介紹一個(gè)方便好用的函數(shù):
# 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
spath="D:/download/baa.txt" f=open(spath,"w") # Opens file for writing.Creates this file doesn't exist. f.write("First line 1.\n") f.writelines("First line 2.") f.close() f=open(spath,"r") # Opens file forreading for line in f: print line f.close()
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!"
class Base: def __init__(self): self.data =[] def add(self, x): self.data.append(x) def addtwice(self, x): self.add(x) self.add(x) # Child extends Base class Child(Base): def plus(self,a,b): return a+b oChild =Child() oChild.add("str1") print oChild.data print oChild.plus(2,3)
每一個(gè).py文件稱為一個(gè)module,module之間可以互相導(dǎo)入.請(qǐng)參看以下例子:
# a.py def add_func(a,b): return a+b
# b.py from a import add_func # Also can be : import a print "Import add_func from module a" print"Result of 1 plus 2 is: " print add_func(1,2) # If using "import a" , then here should be "a.add_func"
module可以定義在包里面.Python定義包的方式稍微有點(diǎn)古怪,假設(shè)我們有一個(gè)parent文件夾,該文件夾有一個(gè)child子文件夾.child中有一個(gè)module a.py . 如何讓Python知道這個(gè)文件層次結(jié)構(gòu)?很簡(jiǎn)單,每個(gè)目錄都放一個(gè)名為_(kāi)init_.py 的文件.該文件內(nèi)容可以為空.這個(gè)層次結(jié)構(gòu)如下所示:
parent
--__init_.py
--child
-- __init_.py
--a.pyb.py
那么Python如何找到我們定義的module?在標(biāo)準(zhǔn)包sys中,path屬性記錄了Python的包路徑.你可以將之打印出來(lái):
import sys print sys.path
通常我們可以將module的包路徑放到環(huán)境變量PYTHONPATH中,該環(huán)境變量會(huì)自動(dòng)添加到sys.path屬性.另一種方便的方法是編程中直接指定我們的module路徑到sys.path 中:
import sys sys.path.append('D:\\download') from parent.child.a import add_func print sys.path print "Import add_func from module a" print"Result of 1 plus 2 is: " print add_func(1,2)
這個(gè)教程很簡(jiǎn)單,其中包含了很多Python的特性在代碼中顯露出來(lái),這些特性包括Python是不需要顯式聲明數(shù)據(jù)類型,關(guān)鍵字說(shuō)明,字符串函數(shù)的解釋等等.通過(guò)這個(gè)文章可以盡快熟悉Python,然后盡快能用它開(kāi)始編程
標(biāo)簽:安慶 吉林 岳陽(yáng) 泉州 洛陽(yáng) 清遠(yuǎn) 長(zhǎng)春 怒江
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