[英]Python: Find the list element that is contained least times in another list
So I have a list of possible elments: 因此,我列出了可能的要点:
elems = ['a', 'b', 'c', 'd']
Then I have another list of random items chosen from the first list. 然后,我从第一个列表中选择了另一个随机项目列表。
Something like (for example): 类似于(例如)的东西:
items = ['a', 'a', 'c', 'a', 'c', 'd']
What is the Pythonic way to find out which element in elems
is contained least often in items
? 什么是Python的方式,以找出哪些元素
elems
包含至少经常items
?
In this example it is 'b'
, because that's not contained in items
at all. 在此示例中,它是
'b'
,因为它根本不包含在items
中。
Short 短
print(min(elems, key=items.count)) # b
Relatively short and efficient (only use it if you're sure there're no duplicates in elems
) 相对简短高效 (仅当您确定
elems
没有重复项时才使用它)
from collections import Counter
c = Counter(items + elems)
print(c.most_common()[-1][0]) # b
Just efficient 高效
d = {x: 0 for x in elems}
for x in items:
d[x] += 1
print(min(d, key=d.get)) # b
Another "just efficient" 另一个“效率高”
from collections import defaultdict
d = defaultdict(int)
for x in items:
d[x] += 1
print(min(elems, key=d.__getitem__))
# or print(min(elems, key=lambda x: d[x])) - gives same result
>>> from collections import Counter
>>> elems = ['a', 'b', 'c', 'd']
>>> items = ['a', 'a', 'c', 'a', 'c', 'd']
>>> c = Counter(dict.fromkeys(elems, 0))
>>> c.update(Counter(items))
>>> c
Counter({'a': 3, 'c': 2, 'd': 1, 'b': 0})
>>> min(c, key=c.get)
'b'
The fastest way is to make a dictionary with counts in it: 最快的方法是制作一个包含数字的字典:
aDict = { k:0 for k in elems }
for x in items:
if x not in aDict: aDict[x] = 0
aDict[x] += 1
print min(aDict, key=aDict.get)
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