Python：如何按最常见的第一个元素对列表进行排序？

如何按第一个元素的数量对列表进行排序？例如，如果我在下面列出了以下列表，我希望将列表排序，以便所有的“格鲁吉亚大学”参赛作品排在第一位，然后是“密歇根大学”参赛作品，然后是“佛罗里达大学”条目。Python：如何按最常见的第一个元素对列表进行排序？

l = [['University of Michigan','James Jones','phd'], 
    ['University of Georgia','Anne Greene','ba'], 
    ['University of Michigan','Frank Kimball','ma'], 
    ['University of Florida','Nate Franklin','ms'], 
    ['University of Georgia','Sara Dean','ms'], 
    ['University of Georgia','Beth Johnson','bs']]

来源

2014-02-27 user3314445

from collections import Counter 
c = Counter(item[0] for item in l) 
print sorted(l, key = lambda x: -c[x[0]])

输出

[['University of Georgia', 'Anne Greene', 'ba'], 
['University of Georgia', 'Sara Dean', 'ms'], 
['University of Georgia', 'Beth Johnson', 'bs'], 
['University of Michigan', 'James Jones', 'phd'], 
['University of Michigan', 'Frank Kimball', 'ma'], 
['University of Florida', 'Nate Franklin', 'ms']]

香草字典版本：

c = {} 
for item in l: 
    c[item[0]] = c.get(item[0], 0) + 1 
print sorted(l, key = lambda x: -c[x[0]])

defaultdict版本：

from collections import defaultdict 
c = defaultdict(int) 
for item in l: 
    c[item[0]] += 1 
print sorted(l, key = lambda x: -c[x[0]])

来源

2014-02-27 15:54:08 thefourtheye

+1从u学到很多东西;） – zhangxaochen

@zhangxaochen欢迎您:)你善于numpy的自己:) – thefourtheye

待办事项不要忘记，Python 2.6.6中不存在Counter，因此如果以后的Python不可用，就不能使用它。 – sabbahillel

-1

从这里获取解决方案：How to sort a list of lists by a specific index of the inner list?

from operator import itemgetter 

L=[['University of Michigan','James Jones','phd'],['University of Georgia','Anne Greene','ba'],['University of Michigan','Frank Kimball','ma'],['University of Florida','Nate Franklin','ms'],['University of Georgia','Sara Dean','ms'],['University of Georgia','Beth Johnson','bs']] 

print 'Before:', L 
print ' After:', sorted(L, key=itemgetter(0))

输出

Before: [['University of Michigan', 'James Jones', 'phd'], ['University of Georgia', 'Anne Greene', 'ba'], ['University of Michigan', 'Frank Kimball', 'ma'], ['University of Florida', 'Nate Franklin', 'ms'], ['University of Georgia', 'Sara Dean', 'ms'], ['University of Georgia', 'Beth Johnson', 'bs']] 
After: [['University of Florida', 'Nate Franklin', 'ms'], ['University of Georgia', 'Anne Greene', 'ba'], ['University of Georgia', 'Sara Dean', 'ms'], ['University of Georgia', 'Beth Johnson', 'bs'], ['University of Michigan', 'James Jones', 'phd'], ['University of Michigan', 'Frank Kimball', 'ma']]

来源

2014-02-27 16:07:09 quake

Python：如何按最常见的第一个元素对列表进行排序？

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