python 如何在python中将一个列表映射到另一个列表？
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How to map one list to another in python?
提问by user288832
['a','a','b','c','c','c']
to
到
[2, 2, 1, 3, 3, 3]
and
和
{'a': 2, 'c': 3, 'b': 1}
回答by YOU
>>> x=['a','a','b','c','c','c']
>>> map(x.count,x)
[2, 2, 1, 3, 3, 3]
>>> dict(zip(x,map(x.count,x)))
{'a': 2, 'c': 3, 'b': 1}
>>>
回答by Juergen
This coding should give the result:
此编码应给出结果：
from collections import defaultdict
myDict = defaultdict(int)
for x in mylist:
myDict[x] += 1
Of course if you want the list inbetween result, just get the values from the dict (mydict.values()).
当然，如果您想要结果之间的列表，只需从字典（mydict.values()）中获取值。
回答by Mizipzor
Use a setto only count each item once, use the list method countto count them, store them in a dictwith the item as key and the occurrence is value.
使用aset只对每个item计数一次，使用list方法count计数，dict以item为key存储在a中，出现次数为value。
l=["a","a","b","c","c","c"]
d={}
for i in set(l):
d[i] = l.count(i)
print d
Output:
输出：
{'a': 2, 'c': 3, 'b': 1}
回答by kennytm
On Python ≥2.7 or ≥3.1, we have a built-in data structure collections.Counterto tally a list
在 Python ≥2.7 或 ≥3.1 上，我们有一个内置的数据结构collections.Counter来统计一个列表
>>> l = ['a','a','b','c','c','c']
>>> Counter(l)
Counter({'c': 3, 'a': 2, 'b': 1})
It is easy to build [2, 2, 1, 3, 3, 3]afterwards.
[2, 2, 1, 3, 3, 3]之后很容易建立。
>>> c = _
>>> [c[i] for i in l] # or map(c.__getitem__, l)
[2, 2, 1, 3, 3, 3]
回答by luc
a = ['a','a','b','c','c','c']
b = [a.count(x) for x in a]
c = dict(zip(a, b))
I've included Wim answer. Great idea
我已经包含了 Wim 的答案。好点子
回答by Wim
Second one could be just
第二个可能只是
dict(zip(['a','a','b','c','c','c'], [2, 2, 1, 3, 3, 3]))
回答by JonT
For the first one:
对于第一个：
l = ['a','a','b','c','c','c']
l = ['a','a','b','c','c','c']
map(l.count,l)
地图（l.count，l）
回答by starhusker
d=defaultdict(int)
for i in list_to_be_counted: d[i]+=1
l = [d[i] for i in list_to_be_counted]
