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5.1.4 Á´±íÍƵ¼Ê½ 
Á´±íÍƵ¼Ê½ÌṩÁËÒ»¸ö´´½¨Á´±íµÄ¼òµ¥Í¾¾¶£¬ÎÞÐèʹÓà map()£¬ filter() ÒÔ¼° lambda¡£·µ»ØÁ´±íµÄ¶¨Òåͨ³£Òª±È´´½¨ÕâЩÁ´±í¸üÇåÎú¡£Ã¿Ò»¸öÁ´±íÍƵ¼Ê½°üÀ¨ÔÚÒ»¸öforÓï¾äÖ®ºóµÄ±í´ïʽ£¬Áã»ò¶à¸öfor»òifÓï¾ä¡£·µ»ØÖµÊÇÓÉfor»òif×Ó¾äÖ®ºóµÄ±í´ïʽµÃµ½µÄÔªËØ×é³ÉµÄÁ´±í¡£Èç¹ûÏëÒªµÃµ½Ò»¸öÔª×飬±ØÐëÒª¼ÓÉÏÀ¨ºÅ¡£
>>> freshfruit = ['  banana', '  loganberry ', 'passion fruit  ']
>>> [weapon.strip() for weapon in freshfruit]
['banana', 'loganberry', 'passion fruit']
>>> vec = [2, 4, 6]
>>> [3*x for x in vec]
[6, 12, 18]
>>> [3*x for x in vec if x > 3]
[12, 18]
>>> [3*x for x in vec if x < 2]
[]
>>> [[x,x**2] for x in vec]
[[2, 4], [4, 16], [6, 36]]
>>> [x, x**2 for x in vec]      # error - parens required for tuples
  File "", line 1, in ?
    [x, x**2 for x in vec]
               ^
SyntaxError: invalid syntax
>>> [(x, x**2) for x in vec]
[(2, 4), (4, 16), (6, 36)]
>>> vec1 = [2, 4, 6]
>>> vec2 = [4, 3, -9]
>>> [x*y for x in vec1 for y in vec2]
[8, 6, -18, 16, 12, -36, 24, 18, -54]
>>> [x+y for x in vec1 for y in vec2]
[6, 5, -7, 8, 7, -5, 10, 9, -3]
>>> [vec1[i]*vec2[i] for i in range(len(vec1))]
[8, 12, -54]
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>>> x = 100                     # this gets overwritten
>>> [x**3 for x in range(5)]
[0, 1, 8, 27, 64]
>>> x                           # the final value for range(5)
4

======== 2005-05-07 14:12:00 ÄúÔÚÀ´ÐÅÖÐдµÀ£º ========

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listone = [2, 3, 4]
listtwo = [2*i for i in listone if i > 2]
print listtwo

Êä³öÈçÏ£º
[4, 6, 8]

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¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2005-05-07
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