Python入门教程 超详细1小时学会Python

大型商业网站或者设计复杂的游戏,悉听尊便. --------------------------------------------------------------------- 2 快速入门2.1 Hello world 安装完Python之后(我本机的版本是2.5.4),打开IDLE(Python GUI) , 该程序是Python语言解释器,你写的语句能够立即运行.我们写下一句著名的程序语句: print "Hello,world!" 并按回车.你就能看到这句被K&R引入到程序世界的名言. 在解释器中选择"File"--"New Window" 或快捷键 Ctrl+N , 打开一个新的编辑器.写下如下语句: print "Hello,world!" raw_input("Press enter key to close this window"); 保存为a.py文件.按F5,你就可以看到程序的运行结果了.这是Python的第二种运行方式. 找到你保存的a.py文件,双击.也可以看到程序结果.Python的程序能够直接运行,对比Java,这是一个优势. --------------------------------------------------------------------- 2.2 国际化支持 我们换一种方式来问候世界.新建一个编辑器并写如下代码: print "欢迎来到奥运中国!" raw_input("Press enter key to close this window"); 在你保存代码的时候,Python会提示你是否改变文件的字符集,结果如下: # -*- coding: cp936 -*- print "欢迎来到奥运中国!" raw_input("Press enter key to close this window"); 将该字符集改为我们更熟悉的形式: # -*- coding: GBK -*- print "欢迎来到奥运中国!" # 使用中文的例子 raw_input("Press enter key to close this window"); 程序一样运行良好. --------------------------------------------------------------------- 2.3 方便易用的计算器 用微软附带的计算器来计数实在太麻烦了.打开Python解释器,直接进行计算: a=100.0 b=201.1 c=2343 print (a+b+c)/c --------------------------------------------------------------------- 2.4 字符串,ASCII和UNICODE 可以如下打印出预定义输出格式的字符串: print """ Usage: thingy [OPTIONS] -h Display this usage message -H hostname Hostname to connect to """ 字符串是怎么访问的?请看这个例子: 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) 请注意ASCII和UNICODE字符串的区别: 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); --------------------------------------------------------------------- 2.5 使用List 类似Java里的List,这是一种方便易用的数据类型: word=['a','b','c','d','e','f','g'] a=word[2] print "a is: "+a b=word[1:3] print "b is: " print b # 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. 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 --------------------------------------------------------------------- 2.6 条件和循环语句 # Multi-way decision 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) --------------------------------------------------------------------- 2.7 如何定义函数 # 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,介绍一个方便好用的函数: # 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 --------------------------------------------------------------------- 2.8 文件I/O 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 for reading for line in f: print line f.close() --------------------------------------------------------------------- 2.9 异常处理 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!" --------------------------------------------------------------------- 2.10 类和继承 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) -------------------------------------------------------------------------------- 2.11 包机制 每一个.py文件称为一个module,module之间可以互相导入.请参看以下例子: # 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可以定义在包里面.Python定义包的方式稍微有点古怪,假设我们有一个 parent文件夹,该文件夹有一个child子文件夹.child中有一个module a.py . 如何让Python知道这个文件层次结构?很简单,每个目录都放一个名为 _init_.py 的文件.该文件可以为空.这个层次结构如下所示: parent --__init_.py --child -- __init_.py --a.py b.py 那么Python如何找到我们定义的module?在包sys中,path属性记录了Python的包路径.你可以将之打印出来: import sys print sys.path 通常我们可以将module的包路径放到环境变量PYTHONPATH中,该环境变量会自动添加到sys.path属性.另一种方便的方法是编程中直接指定我们的module路径到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) --------------------------------------------------------------------- 总结你会发现这个教程相当的简单.许多Python特性在代码中以隐含方式提出,这些特性包括:Python不需要显式声明数据类型,关键字说明,字符串函数的解释等等.我认为一个熟练的程序员应该对这些概念相当了解,这样在你挤出宝贵的一小时阅读这篇短短的教程之后,你能够通过已有知识的迁移类比尽快熟悉Python,然后尽快能用它开始编程.