【Python学习日记】函数列表 动态创建函数 文件读取 迭代器

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

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

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

　　程序代码

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

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

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'));