Python 交换列表中的第一个和最后一个项目
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Swapping first and last items in a list
提问by user2891763
How can I go about swapping numbers in a given list?
如何交换给定列表中的数字？
For example:
例如：
list = [5,6,7,10,11,12]
I would like to swap 12with 5.
我想12与5.
Is there an built-in Python function that can allow me to do that?
是否有内置的 Python 函数可以让我这样做？
回答by Ashwini Chaudhary
>>> lis = [5,6,7,10,11,12]
>>> lis[0], lis[-1] = lis[-1], lis[0]
>>> lis
[12, 6, 7, 10, 11, 5]
Order of evaluationof the above expression:
上述表达式的求值顺序：
expr3, expr4 = expr1, expr2
First items on RHS are collected in a tuple, and then that tuple is unpackedand assigned to the items on the LHS.
RHS 上的第一个项目被收集在一个元组中，然后该元组被解包并分配给 LHS 上的项目。
>>> lis = [5,6,7,10,11,12]
>>> tup = lis[-1], lis[0]
>>> tup
(12, 5)
>>> lis[0], lis[-1] = tup
>>> lis
[12, 6, 7, 10, 11, 5]
回答by jramirez
Use the index of the number you want to change.
使用您要更改的号码的索引。
In [38]: t = [5,6,7,10,11,12]
In [40]: index5 = t.index(5) # grab the index of the first element that equals 5
In [41]: index12 = t.index(12) # grab the index of the first element that equals 12
In [42]: t[index5], t[index12] = 12, 5 # swap the values
In [44]: t
Out[44]: [12, 6, 7, 10, 11, 5]
Then you can make a quick swapping function
然后你可以做一个快速交换功能
def swapNumbersInList( listOfNums, numA, numB ):
indexA = listOfNums.index(numA)
indexB = listOfNums.index(numB)
listOfNums[indexA], listOfNums[indexB] = numB, numA
# calling the function
swapNumbersInList([5,6,7,10,11,12], 5, 12)
回答by Don
Another way (not so cute):
另一种方式（不那么可爱）：
mylist = [5, 6, 7, 10, 11, 12]
first_el = mylist.pop(0) # first_el = 5, mylist = [6, 7, 10, 11, 12]
last_el = mylist.pop(-1) # last_el = 12, mylist = [6, 7, 10, 11]
mylist.insert(0, last_el) # mylist = [12, 6, 7, 10, 11]
mylist.append(first_el) # mylist = [12, 6, 7, 10, 11, 5]
回答by Ashif Abdulrahman
you can swap using this code,
您可以使用此代码进行交换，
list[0],list[-1] = list[-1],list[0]
回答by Harrison Croaker
array = [5,2,3,6,1,12]
temp = ''
lastvalue = 5
temp = array[0]
array[0] = array[lastvalue]
array[lastvalue] = temp
print(array)
Hope this helps :)
希望这可以帮助 ：）
回答by aghd
回答by iBee
This is what finally worked for me.
这就是最终对我有用的方法。
def swap(the_list):
temp = the_list[0]
the_list[0] = the_list[-1]
the_list[-1] = temp
return the_list
