如何在 python 中对元素元组进行排序，首先根据值，然后根据键。考虑我将用户输入作为字符串的程序。我想找出每个字符的数量并打印字符串中最常见的 3 个字符。
#input string
strr=list(raw_input())
count=dict()
#store the count of each character in dictionary
for i in range(len(strr)):
count[strr[i]]=count.get(strr[i],0)+1
#hence we can't perform sorting on dict so convert it into tuple
temp=list()
t=count.items()
for (k,v) in t:
temp.append((v,k))
temp.sort(reverse=True)
#print 3 most common element
for (v,k) in temp[:3]:
print k,v
关于给予 i/p -aabbbccde
以上代码的输出是:
3 b
2 c
2 a
但我希望输出为:
3 b
2 a
2 c
对元组列表进行排序，第一个值按降序排列(reverse=True)，第二个值按升序排列(reverse=False，默认情况下)。这是一个 MWE。
lists = [(2, 'c'), (2, 'a'), (3, 'b')]
result = sorted(lists, key=lambda x: (-x[0], x[1])) # -x[0] represents descending order
print(result)
# Output
[(3, 'b'), (2, 'a'), (2, 'c')]
使用起来很简单collections.Counter
计算字符串中每个字母的频率。
import collections
s = 'bcabcab'
# If you don't care the order, just use `most_common`
#most_common = collections.Counter(s).most_common(3)
char_and_frequency = collections.Counter(s)
result = sorted(char_and_frequency.items(), key=lambda x:(-x[1], x[0]))[:3] # sorted by x[1] in descending order, x[0] in ascending order
print(result)
# Output
[('b', 3), ('a', 2), ('c', 2)]