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Python内置函数——set&frozenset

黄舟

发布： 2017-01-19 16:35:07

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Python内置函数——set&frozenset

set

set()
set对象实例化
>>> set(&#39;add&#39;)
set([&#39;a&#39;, &#39;d&#39;])
>>> set(&#39;python&#39;).add(&#39;hello&#39;)
>>> print set(&#39;python&#39;).add(&#39;hello&#39;)
None
>>> a = set(&#39;python&#39;)
>>> a
set([&#39;h&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;])
>>> a.add(&#39;hello&#39;)
>>> a
set([&#39;h&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;, &#39;hello&#39;])
>>> a.update(&#39;python&#39;)
>>> a
set([&#39;h&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;, &#39;hello&#39;])
>>> a.update(&#39;hello&#39;)
>>> a
set([&#39;e&#39;, &#39;h&#39;, &#39;l&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;, &#39;hello&#39;])
>>> a.remove(&#39;hello&#39;)
>>> a
set([&#39;e&#39;, &#39;h&#39;, &#39;l&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;])
>>> b = set(&#39;hello&#39;)
>>> b
set([&#39;h&#39;, &#39;e&#39;, &#39;l&#39;, &#39;o&#39;])
>>> a - b
set([&#39;y&#39;, &#39;p&#39;, &#39;t&#39;, &#39;n&#39;])
>>> a & b
set([&#39;h&#39;, &#39;e&#39;, &#39;l&#39;, &#39;o&#39;])
>>> a | b
set([&#39;e&#39;, &#39;h&#39;, &#39;l&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;t&#39;, &#39;y&#39;])
>>> a != b
True
>>> a == b
False
>>> b in a
False
>>> a in b
False
>>> c = set(&#39;hell&#39;)
>>> c in b
False
>>> b
set([&#39;h&#39;, &#39;e&#39;, &#39;l&#39;, &#39;o&#39;])
>>> c
set([&#39;h&#39;, &#39;e&#39;, &#39;l&#39;])
>>> &#39;h&#39; in c
True
>>> &#39;p&#39; in c
False

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frozenset

frozenset([iterable])
产生一个不可变的set
>>> a = frozenset(range(10))
>>> a
frozenset([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> a.remove(0)
Traceback (most recent call last):
  File "<pyshell#189>", line 1, in <module>
    a.remove(0)
AttributeError: &#39;frozenset&#39; object has no attribute &#39;remove&#39;
>>> b = set(range(10))
>>> b
set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> b.remove(1)
>>> b
set([0, 2, 3, 4, 5, 6, 7, 8, 9])

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