python 生成器迭代器用法最全总结(7种典型的用法)

蔚落 2022-01-21 02:45 194阅读 0赞

## 1.利用\_\_getitem\_\_()让编译器自动遍历生成 ##

import re #后面省略书写
    
    RE_WORD = re.compile('\w+')#后面省略书写
    
    class Sentence1:
    
        def __init__(self,text):
            self.text = text
            self.words = RE_WORD.findall(text)#返回匹配列表
        def __getitem__(self,index):
            return self.words[index]
    
    s1 = Sentence1('"the time make god and gost" mir ding said') #可遍历输出

## 2.利用\_\_iter\_\_()调用 自定义类型 的生成器函数 ##

class Sentence2:
        def __init__(self,text):
            self.text = text
            self.words = RE_WORD.findall(text)
        def __iter__(self):
            return iter(self.words)#利用列表的__iter__返回生成器
    
    s2 = Sentence2('"the time make god and gost" mir ding said')#可遍历输出

## 3.典型的方法（啰嗦但是却标准的无可反驳，不是懒人的做法） ##

class Sentence3:
    
        def __init__(self,text):
            self.text = text
            self.words = RE_WORD.findall(text)
        def __iter__(self):
            return Sentence3Iterator(self.words)#利用对应的生成器类，实例化生成器对象
    
    class Sentence3Iterator:
        
        def __init__(self,words_list):
            self.words_list = words_list
            self.pos = 0
        def __next__(self):
            try:
                word = self.words_list[self.pos]
            except IndexError:
                raise StopIteration()
            self.pos +=1
            return word
        def __iter__(self):
            return self
    
    s3 = Sentence3('"the time make god and gost" mir ding said')#可遍历输出

## 4.利用生成器函数yield 简单高效 ##

class Sentence4:
    
        def __init__(self,text):
            self.text = text  #拷贝的引用，并不占用太多内存
            self.words = RE_WORD.findall(text)#建立所有单词的列表，占用大量内存，接下来优化
        def __iter__(self):
            for word in self.words:
                yield word
            return  #可有可无
        
    s4 = Sentence4('"the time make god and gost" mir ding said')#可遍历输出

## 5.惰性实现，节省内存 ##

class Sentence5:
    
        def __init__(self,text):
            self.text = text  
            
        def __iter__(self):
            for word in RE_WORD.finditer(self.text):#finditer返回一个迭代器
                yield word.group()
            return  
        
    s5 = Sentence5('"the time make god and gost" mir ding said')#可遍历输出

## 6.利用生成器表达式进一步简化，生成器表达式返回一个新的生成器 ##

class Sentence6:
    
        def __init__(self,text):
            self.text = text  
            
        def __iter__(self):
            return  ( word.group() for word in RE_WORD.finditer(self.text)) #语法糖跟生成器函数一样
        
    s6 = Sentence6('"the time make god and gost" mir ding said')#可遍历输出

## 7.yield from (整个迭代器"搬过来"用) ##

class Sentence7:
    
        def __init__(self,text,text_added):
            self.text = text  
            self.text_added = text_added
        def __iter__(self):
                yield from ( word.group() for word in RE_WORD.finditer(self.text))
                yield from ( word.group() for word in RE_WORD.finditer(self.text_added))
        
    s7 = Sentence7('"the time make god and gost" mir ding said',"conclusion: i love time")#可遍历输出