Python进阶——迭代器和可迭代对象有什么区别？

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开发中，我们经常听到有关「容器」、「迭代器」、「可迭代对象」、「生成器」的概念。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我们经常把这些概念搞混淆，它们之间有哪些联系和区别呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这篇文章，我们就来看一下它们之间的关系。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"容器","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，我们先来看一下容器是如何定义的？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"简单来说，容器就是存储某些元素的统称，它最大的特性就是判断一个元素是否在这个容器内。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"怎么理解这句话？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"很简单，在 Python 中，我们通常使用 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"in","attrs":{}}],"attrs":{}},{"type":"text","text":" 或 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"not in","attrs":{}}],"attrs":{}},{"type":"text","text":" 来判断一个元素存在/不存在于一个容器内。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如下面这个例子：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"python"},"content":[{"type":"text","text":"print('x' in 'xyz') # True\nprint('a' not in 'xyz') # True\nprint(1 in [1, 2, 3]) # True\nprint(2 not in (1, 2, 3)) # False\nprint('x' not in {'a', 'b', 'c'}) # True\nprint('a' in {'a': 1, 'b': 2}) # 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方法，那么它就是一个「容器」。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我们在开发时，除了使用 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"in","attrs":{}}],"attrs":{}},{"type":"text","text":" 判断元素是否在容器内之外，另外一个常用的功能是：输出容器内的所有元素。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如执行 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"for x in [1, 2, 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的方式迭代出容器内的所有数据，这就需要这个类实现「迭代器协议」。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"也就是说，一个类如果实现了「迭代器协议」，就可以称之为「迭代器」。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"什么是「迭代器协议」呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在 Python 中，实现迭代器协议就是实现以下 2 个方法：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"__iter__","attrs":{}}],"attrs":{}},{"type":"text","text":"：这个方法返回对象本身，即 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"self","attrs":{}}],"attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"__next__","attrs":{}}],"attrs":{}},{"type":"text","text":"：这个方法每次返回迭代的值，在没有可迭代元素时，抛出 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"StopIteration","attrs":{}}],"attrs":{}},{"type":"text","text":" 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因为它把迭代细节交给了A\nb = B(3)\nfor i in b:\n print(i)\n# <__main__.a object="" at="">\nprint(iter(b))","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"仔细看这个例子，我们定义了 2 个类 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"A","attrs":{}}],"attrs":{}},{"type":"text","text":" 和 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"B","attrs":{}}],"attrs":{}},{"type":"text","text":"，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"A","attrs":{}}],"attrs":{}},{"type":"text","text":" 实现了 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"iter","attrs":{}}],"attrs":{}},{"type":"text","text":" 和 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