问题描述
c2=[]
row1=[1,22,53]
row2=[14,25,46]
row3=[7,8,9]
c2.append(row2)
c2.append(row1)
c2.append(row3)
c2
现在是:
[[14, 25, 46], [1, 22, 53], [7, 8, 9]]
我该如何对c2
进行排序,例如:
how do i sort c2
in such a way that for example:
for row in c2:
sort on row[2]
结果将是:
[[7,8,9],[14,25,46],[1,22,53]]
另一个问题是我如何首先按行[2]排序,并在其中按行[1]设置
the other question is how do i first sort by row[2] and within that set by row[1]
推荐答案
sort
的key
参数指定一个参数的功能,该参数用于从每个列表元素中提取比较键.因此,我们可以创建一个简单的lambda
,该lambda
返回每行中要在排序中使用的最后一个元素:
The key
argument to sort
specifies a function of one argument that is used to extract a comparison key from each list element. So we can create a simple lambda
that returns the last element from each row to be used in the sort:
c2.sort(key = lambda row: row[2])
一个lambda
是一个简单的匿名函数.当您想创建一个像这样的简单一次性功能时.不使用lambda
的等效代码为:
A lambda
is a simple anonymous function. It's handy when you want to create a simple single use function like this. The equivalent code not using a lambda
would be:
def sort_key(row):
return row[2]
c2.sort(key = sort_key)
如果要对更多条目进行排序,只需使key
函数返回一个元组,其中包含要按重要性顺序排序的值.例如:
If you want to sort on more entries, just make the key
function return a tuple containing the values you wish to sort on in order of importance. For example:
c2.sort(key = lambda row: (row[2],row[1]))
或:
c2.sort(key = lambda row: (row[2],row[1],row[0]))
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