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清风; 100%

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概述

Python除了语言简洁,容易上手等优点,还有一个重要的优点,就是存在大量的内置函数,方便编程.这个章节将介绍这些常用函数.让您更好的了解Python的诱人之处.

使用

enumerate

enumerate是python 2.3中新增的内置函数，它的英文说明为：

enumerate(iterable)
    Return an enumerate object. iterable must be a sequence, an iterator, or some other object which supports iteration. The next() method of the iterator returned by enumerate() returns a tuple containing a count (from zero) and the corresponding value obtained from iterating over iterable. enumerate() is useful for obtaining an indexed series: (0, seq[0]), (1, seq[1]), (2, seq[2]), .... New in version 2.3.

它特别适合用于一个for循环时，当我们同时需要计数和元素时可以使用这个函数。举个简单的例子，有一个字符串数组，需要一行一行打印出来，同时每行前面加上计数，从1开始。

例如:

   1 mylist=["a","b","c"]
   2 for index,obj in enumerate(mylist):
   3     print index,obj

0,"a"
1,"b"
2,"c"

map

行者:以一个小例子,展示map的威力,将数组中每一个数乘以2

   1 map(lambda x:x*2,[1,2,3,4,5])

行者:同时循环两个一样长的数组

   1 for x,y in zip([1,2,3],[4,5,6]):
   2     print "x,y",x,y

行者:过滤掉,数组中小于3的数

   1 filter(lambda x:x>3,[1,2,3,4,5])

-- 清风 DateTime(2008-04-25T14:33:00Z)

-  ⇤ ← Revision 3 as of 2008-06-24 07:38:20 → 
  Size: 1077
  Editor: qingfeng
  Comment:
+   ← Revision 4 as of 2008-08-14 14:02:47 → ⇥
  Size: 1695
  Editor: qingfeng
  Comment:
-Deletions are marked like this.
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-== enumerate ==
小白:Python中的循环,想知道现在循环了几次好麻烦,总要在循环外定义一个变量,然后每次循环再加1,像这样:
+== 概述 ==
Python除了语言简洁,容易上手等优点,还有一个重要的优点,就是存在大量的内置函数,方便编程.这个章节将介绍这些常用函数.让您更好的了解Python的诱人之处.

== 使用 ==
=== enumerate ===
enumerate是python 2.3中新增的内置函数，它的英文说明为：
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-i=0
for obj in objlist:
    i+=1
    print i
+enumerate(iterable)
    Return an enumerate object. iterable must be a sequence, an iterator, or some other object which supports iteration. The next() method of the iterator returned by enumerate() returns a tuple containing a count (from zero) and the corresponding value obtained from iterating over iterable. enumerate() is useful for obtaining an indexed series: (0, seq[0]), (1, seq[1]), (2, seq[2]), .... New in version 2.3.
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+Line 19:
-行者:..........请尝试enumerate
+它特别适合用于一个for循环时，当我们同时需要计数和元素时可以使用这个函数。举个简单的例子，有一个字符串数组，需要一行一行打印出来，同时每行前面加上计数，从1开始。

例如:
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+Line 32:
-== 其他内置函数 ==
 * 小白:enumerate很方便,那Python还有什么内置函数吗?
 * 行者:map,zip,filter,等等,很多.
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-== 练习 ==