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    Python数据分析(中英对照)·Dictionaries 字典

    字典是从键对象到值对象的映射。 Dictionaries are mappings from key objects to value objects. 字典由键:值对组成,其中键必须是不可变的,值可以是任何值。 Dictionaries consists of Key:Value pairs, where the keys must be immutable and the values can be anything. 词典本身是可变的,因此这意味着一旦创建词典,就可以动态修改其内容。 Dictionaries themselves are mutable so this means once you create your dictionary, you can modify its contents on the fly. 字典可用于对无序数据执行非常快速的查找。 Dictionaries can be used for performing very fast look-ups on unordered data. 关于词典,需要注意的一个关键方面是它们不是序列,因此不保持任何类型的左右顺序。 A key aspect to be aware about regarding dictionaries is that they are not sequences, and therefore do not maintain any type of left-right order. 这意味着,如果在字典上循环,Key:Value对将以任意顺序迭代。 This means that if you’re looping over a dictionary,the Key:Value pairs will be iterated over in arbitrary order. 让我们看一个图表来阐明这个观点。 Let’s look at a diagram to clarify this idea. 我们将建立一个简单的字典,其中有与value对象关联的第一个键。 We’re going to set up a simple dictionary where we have our first key that’s associated with a value object. 我们有第二把钥匙,和另一个物体在一起。 We have our second key that goes with another object. 假设我们这里有第四个键,它和相应的值对象一起。 And let’s say we have key number four here which goes with the corresponding value object. 如果这是一个字典,那么这个键对象将始终与这个值对象相关联。 If this is a dictionary, this key object will always be associated with this value object. 类似地,此键将始终与此值对象一起使用。 Similarly, this key will always go with this value object. 当我们说字典不维护任何类型的左或右顺序时,我们所说的是这些键值对本身的顺序没有定义。 When we say that dictionaries don’t maintain any type of left or right order, what we’re saying is that the ordering of these key-value pairs themselves is not defined. 这意味着如果我在这些对上循环,我可能首先得到对应于我的第二个密钥的对。 That means if I’m looping over these pairs,I might first get the pair that corresponds to my second key here. 然后让我们看看字典的一些用法。 Let’s then look at some uses of dictionaries. 我想编一本叫做《年龄》的字典。 I would like to set up a dictionary which is called age. 如果我希望这是一个空字典,我有两种方法来构造它。 And if I want this to be an empty dictionary,I have two ways to construct that. 第一种方法是只使用一对花括号,这会给

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