如何使用itemgetter对列表进行排序

Question

from operator import itemgetter

c = [['29325493', '491963279'], ['665431604', '107866412'],
    ['572747824', '834468627'], ['623075369', '146360674'],
    ['958964458', '525879903'], ['977175138', '523647968'],
    ['689471337', '580279579'], ['664237570', '288339955'],
    ['328743490', '207620319'], ['315386742', '528392695'],
    ['95567418', '163424206'], ['873955477', '450413794'],
    ['7616943', '842564675'], ['575682685', '33126205'],
    ['89779405', '844288987']]

c.sort(key=itemgetter(0),reverse=True)
print(c)

我试图通过获取每个小列表中的第一项来对列表进行排序。但是，我没有得到正确的答案，而是得到了以下结果：

[['977175138', '523647968'],['958964458', '525879903'],
['95567418', '163424206'], ['89779405', '844288987'],
['873955477', '450413794'], ['7616943', '842564675'],
['689471337', '580279579'], ['665431604', '107866412'],
['664237570', '288339955'], ['623075369', '146360674'],
['575682685', '33126205'], ['572747824', '834468627'],
['328743490', '207620319'], ['315386742', '528392695'],
['29325493', '491963279']]

问题是列表是按每个小列表中项目1的第一个字符排序的。例如，89779405小于873955477。

我该如何解决这个问题？

Answer 1

您需要将子列表转换为整数列表，如下所示：

c = [[int(elem) for elem in l] for l in c]
c.sort(key=itemgetter(0),reverse=True)

或者使用将元素转换为整数的键函数：

c.sort(key=lambda l:int(l[0]),reverse=True)

我不认为在第二种情况下使用itemgetter是有意义的，因为没有内置的函数复合运算符，所以可以编写int o itemgetter(0)。

Answer 2

您可以传递一个将列表的第一个元素转换为int再转换为key的lambda (未命名函数)。

c = [['29325493', '491963279'], ['665431604', '107866412'],
    ['572747824', '834468627'], ['623075369', '146360674'],
    ['958964458', '525879903'], ['977175138', '523647968'],
    ['689471337', '580279579'], ['664237570', '288339955'],
    ['328743490', '207620319'], ['315386742', '528392695'],
    ['95567418', '163424206'], ['873955477', '450413794'],
    ['7616943', '842564675'], ['575682685', '33126205'],
    ['89779405', '844288987']]
c.sort(key=lambda x: int(x[0]), reverse=True)
print(c)

Answer 3

我想，这是你需要的，

from operator import itemgetter


sorted(c, key=itemgetter(0,0))