Python内置函数——set&frozenset
set() set对象实例化 >>> set('add') set(['a', 'd']) >>> set('python').add('hello') >>> print set('python').add('hello') None >>> a = set('python') >>> a set(['h', 'o', 'n', 'p', 't', 'y']) >>> a.add('hello') >>> a set(['h', 'o', 'n', 'p', 't', 'y', 'hello']) >>> a.update('python') >>> a set(['h', 'o', 'n', 'p', 't', 'y', 'hello']) >>> a.update('hello') >>> a set(['e', 'h', 'l', 'o', 'n', 'p', 't', 'y', 'hello']) >>> a.remove('hello') >>> a set(['e', 'h', 'l', 'o', 'n', 'p', 't', 'y']) >>> b = set('hello') >>> b set(['h', 'e', 'l', 'o']) >>> a - b set(['y', 'p', 't', 'n']) >>> a & b set(['h', 'e', 'l', 'o']) >>> a | b set(['e', 'h', 'l', 'o', 'n', 'p', 't', 'y']) >>> a != b True >>> a == b False >>> b in a False >>> a in b False >>> c = set('hell') >>> c in b False >>> b set(['h', 'e', 'l', 'o']) >>> c set(['h', 'e', 'l']) >>> 'h' in c True >>> 'p' in c False
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: 'frozenset' object has no attribute 'remove' >>> 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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