python消除序列的重复值并保持顺序不变的实例


						python 消除序列的重复值，并保持原来顺序

1、如果仅仅消除重复元素，可以简单的构造一个集合





$ python

Python 3.5.2 (default, Nov 23 2017, 16:37:01) 

[GCC 5.4.0 20160609] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> a = [1 , 3, 5, 1, 8, 1, 5]

>>> set(a)

{8, 1, 3, 5}

>>> 



2、利用集合或者生成器解决：值必须是hashable类型





$ python

Python 3.5.2 (default, Nov 23 2017, 16:37:01) 

[GCC 5.4.0 20160609] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> def dupe(items):

... seen = set()

... for item in items:

... if item not in seen:

... yield item

... seen.add(item)

... 

>>> a = [1 , 3, 5, 1, 8, 1, 5]

>>> list(dupe(a))

[1, 3, 5, 8]

>>>



3、消除元素不可哈希：如字典类型





Python 3.5.2 (default, Nov 23 2017, 16:37:01) 

[GCC 5.4.0 20160609] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> def rem(items, key=None):

... seen = set()

... for item in items:

... va = item if key is None else key(item)

... if va not in seen:

... yield item

... seen.add(va)

... 

>>> a = [ {'x':1, 'y':2}, {'x':1, 'y':3}, {'x':1, 'y':2}, {'x':2, 'y':4}]>>> list(rem(a, key=lambda d: (d['x'],d['y'])))

[{'y': 2, 'x': 1}, {'y': 3, 'x': 1}, {'y': 4, 'x': 2}]

>>> list(rem(a, key=lambda d: d['x']))

[{'y': 2, 'x': 1}, {'y': 4, 'x': 2}]



>>>>>> #lambda is an anonymous function:

... fuc = lambda : 'haha'

>>> print (f())

>>> print (fuc())

haha

>>> 







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