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>>> import re >>> re.search(‘[abc]‘,‘mark‘) <_sre.SRE_Match object; span=(1, 2), match=‘a‘> >>> re.sub(‘[abc]‘,‘o‘,‘Mark‘) ‘Mork‘ >>> re.sub(‘[abc]‘,‘o‘, ‘carp‘) ‘oorp‘
import re def plural(noun): if re.search(‘[sxz]$‘,noun): return re.sub(‘$‘,‘es‘,noun) elif re.search(‘[^aeioudgkprt]h$‘,noun): return re.sub(‘$‘,‘es‘,noun) elif re.search(‘[^aeiou]y$‘,noun): return re.sub(‘y$‘,‘ies‘,noun) else: return noun+‘s‘
注：
[abc] --匹配a，b，c中的任何一个字符
[^abc] -- 匹配除了a，b，c的任何字符
>>> import re >>> re.search(‘[^aeiou]y$‘,‘vancancy‘) <_sre.SRE_Match object; span=(6, 8), match=‘cy‘> >>> re.sub(‘y$‘,‘ies‘,‘vacancy‘) ‘vacancies‘ >>> re.sub(‘([^aeiou])y$‘,r‘\1ies‘,‘vacancy‘) ‘vacancies‘
注：
\1-- 表示将第一个匹配到的分组放入该位置。 如果有超过一个分组，则可用\2, \3等等。
函数列表：
a. 在动态函数中使用外部参数值的技术称为闭合。
import re def build_match_and_apply_functions(pattern,search,replace): def matches_rule(word): return re.search(pattern,word) def apply_rule(word): return re.sub(search,replace,word) return (matches_rule,apply_rule)
b.
>>> patterns = ( (‘[sxz]$‘,‘$‘, ‘es‘), (‘[aeioudgkprt]h$‘, ‘$‘, ‘es‘), (‘(qu|[^aeiou])y$‘, ‘y$‘,‘ies‘), (‘$‘, ‘$‘, ‘s‘) ) >>> rules = [build_match_and_apply_functions(pattern, search, replace) for (pattern, search, replace) in patterns] >>> rules [(<function build_match_and_apply_functions.<locals>.matches_rule at 0x10384d510>, <function build_match_and_apply_functions.<locals>.apply_rule at 0x10384d598>), (<function build_match_and_apply_functions.<locals>.matches_rule at 0x10384d620>, <function build_match_and_apply_functions.<locals>.apply_rule at 0x10384d6a8>), (<function build_match_and_apply_functions.<locals>.matches_rule at 0x10384d730>, <function build_match_and_apply_functions.<locals>.apply_rule at 0x10384d7b8>), (<function build_match_and_apply_functions.<locals>.matches_rule at 0x10384d840>, <function build_match_and_apply_functions.<locals>.apply_rule at 0x10384d8c8>)] >>>
c.匹配模式文件
import re def build_match_and_apply_functions(pattern, search,replace): def matches_rule(word): return re.search(pattern,word) def apply_rule(word): return re.sub(search,replace,word) return (matches_rule,apply_rule) rules = [] with open(‘plural4-rules.txt‘, encoding = ‘utf-8‘) as pattern_file: for line in pattern_file: pattern,search,replace = line.split(None,3) rules.append(build_match_and_apply_functions(pattern,search,replace))
1) open():打开文件并返回一个文件对象。
2) ‘with‘:创建了一个context：当with语句结束时，python自动关闭文件，即便是打开是发生意外。
3）split（None,3): None表示对任何空白字符（空格，制表等）进行分隔。3表示针对空白分隔三次，丢弃该行剩下的部分。
生成器：
>>> def make_counter(x): print(‘entering make_counter‘) while True: yield x print(‘incrementing x‘) x=x+1 >>> counter = make_counter(2) >>> counter <generator object make_counter at 0x1038643f0> >>> next(counter) entering make_counter 2 >>> next(counter) incrementing x 3 >>> next(counter) incrementing x 4 >>> next(counter) incrementing x 5
def fib(max): a,b = 0, 1 while a < max : yield a a, b = b, a+b >>> for n in fib(100): print(n,end=‘ ‘) 0 1 1 2 3 5 8 13 21 34 55 89 >>> list(fib(200)) [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144
1)将一个生成器传递给list()函数，它将遍历整个生成器并返回所有生成的数值。
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原文地址：http://www.cnblogs.com/summerlong/p/4482302.html
