【Python学习日记】函数列表 动态创建函数 文件读取 迭代器

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import re   def match_sxz(noun):     return re.search('[sxz]$',noun)   def apply_sxz(noun):     return re.sub('$','es',noun)   def match_h(noun):     return re.search('[^aeioudgkprt]h',noun)   def apply_h(noun):     return re.sub('$','es',noun)   def match_y(noun):     return re.search('[^aeiou]y$',noun)   def apply_y(noun):     return re.sub('y$','ies',noun)   def match_default(noun):     return True   def apply_default(noun):     return re.sub('$','s',noun)   rules = ((match_sxz, apply_sxz),          (match_h, apply_h),          (match_y, apply_y),          (match_default, apply_default)          )   def plural(noun):     for match_rule, apply_rule in rules:         if(match_rule(noun)):             return apply_rule(noun)   print(plural('body'));

改成动态创建函数的方式

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import re   def build_match_apply_function(pattern, search, replace):     def match_rule(word):         return re.search(pattern, word)     def apply_rule(word):         return re.sub(search, replace, word)     return (match_rule, apply_rule)   patterns = \          (              ('[sxz]$','$','es'),              ('[^aeioudgkprt]h$','$','es'),              ('(qu|[^aeiou]y$)','y$','ies'),              ('$','$','s'),              )   rules = [build_match_apply_function(pattern, search, replace)          for (pattern, search, replace) in patterns]   def plural(noun):     for match_rule, apply_rule in rules:         if(match_rule(noun)):             return apply_rule(noun)   print(plural('body'));

　　下面把规则存放到一个文件中，通过读取文件内容的方式，来完成

把规则写到plural.txt中

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[sxz]$          $       es [^aeioudgkprt]h$    $       es [^aeiou]y$      y$      ies $           $       s

　　程序代码

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import re   def build_match_apply_function(pattern, search, replace):     def match_rule(word):         return re.search(pattern, word)     def apply_rule(word):         return re.sub(search, replace, word)     return (match_rule, apply_rule)       rules = []   with open('plural.txt',encoding='gb2312') as pattern_file:     for line in pattern_file:         pattern, search, replace = line.split(None, 3)         rules.append(build_match_apply_function(             pattern, search, replace))   def plural(noun):     for match_rule, apply_rule in rules:         if(match_rule(noun)):             return apply_rule(noun)   print(plural('body'));

　　继续改进，用生成器

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import re   def build_match_apply_function(pattern, search, replace):     def match_rule(word):         return re.search(pattern, word)     def apply_rule(word):         return re.sub(search, replace, word)     return (match_rule, apply_rule)   def rules(rule_filename):     with open(rule_filename,encoding='gb2312') as pattern_file:         for line in pattern_file:             pattern, search, replace = line.split(None, 3)             yield build_match_apply_function(pattern, search, replace)   def plural(noun, rule_filename = 'plural.txt'):     for match_rule, apply_rule in rules(rule_filename):         if(match_rule(noun)):             return apply_rule(noun)     raise ValueError('no matching rule for {0}'.format(noun))   print(plural('body'));

　　改用迭代器读取文件，并缓存

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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]   class LazyRules:     rules_filename = 'plural.txt'       def __init__(self):         self.pattern_file = open(self.rules_filename, encoding='gb2312')         self.cache = []       def __iter__(self):         self.cache_index = 0         return self       def __next__(self):         self.cache_index += 1         if len(self.cache) >= self.cache_index:             return self.cache[self.cache_index - 1]           if self.pattern_file.closed:             raise StopIteration           line = self.pattern_file.readline()         if not line:             self.pattern_file.close()             raise StopIteration           pattern, search, replace = line.split(None, 3)         funcs = build_match_and_apply_functions(             pattern, search, replace)         self.cache.append(funcs)         return funcs   rules = LazyRules()           def plural(noun):     for matches_rule, apply_rule in rules:         if matches_rule(noun):             return apply_rule(noun)   print(plural('bony'));