37 lines
1.6 KiB
Markdown
37 lines
1.6 KiB
Markdown
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---
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title: Python Frozenset
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localeTitle: Python Frozenset
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---
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**`frozenset`基本信息** `frozenset`类型是一个内置的集合类型，它是不可变的和可散列的 - 它的内容在创建后不能被改变;但是，它可以用作字典键或另一组的元素。 Frozensets就像套装一样，只是它们不能改变，即它们是不变的。
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```
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>>> cities = frozenset(["Frankfurt", "Basel", "Freiburg"])
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>>> cities.add("Strasbourg")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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AttributeError: 'frozenset' object has no attribute 'add'
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>>>
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```
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`frozenset`构造函数： `frozenset([iterable])` iterable包含用于初始化frozenset的元素。可以设置iterable，dictionary，tuple等。如果没有传递参数， `frozenset()`方法返回一个空的冻结集。
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**例子**
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```
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>>> vowels = ('a', 'e', 'i', 'o', 'u')
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>>> fSet = frozenset(vowels)
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>>> print("The frozen set is: ", fSet)
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The frozen set is: frozenset({'i', 'e', 'a', 'u', 'o'})
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>>> print("The empty frozen set is: ", frozenset())
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The empty frozen set is: frozenset()
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>>>
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```
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**另一个例子**
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```
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>>> person = {"name": "John", "age": 23, "sex": "male"}
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>>> fSet = frozenset(person)
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>>> print("The frozen set is: ", fSet)
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The frozen set is: frozenset({'sex', 'name', 'age'})
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>>>
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```
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**附加信息** [Python Frozenset（）](https://www.programiz.com/python-programming/methods/built-in/frozenset) [设置类型 - 设置，冷冻设置](https://docs.python.org/2.4/lib/types-set.html) [Python教程：集合和冻结集](https://www.python-course.eu/sets_frozensets.php)
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