"Mok-Kong Shen" <mok-kong.s...@t-online.de> a écrit dans le message de
news:noo1v6$r39$1...@news.albasani.net...
Am 13.08.2016 um 03:08 schrieb Steven D'Aprano:
On Sat, 13 Aug 2016 06:44 am, Mok-Kong Shen wrote:
list2 = [1,2,3]
list1 += [4,5,6]
print(list1, list2)
[1, 2, 3, 4, 5, 6] [1, 2, 3]
Does that help?
I don't yet understand why in my 2nd example list2 came out as
[1, 2, 3] outside.
Because you assign list2 = [1, 2, 3]. What did you expect it to be?
But in my function test() there is a code line "list2=list2+[4,5,6]".
Could you kindly explain why this didn't work?
M. K. Shen
Hello
list1 += [4, 5, 6 ] is slightly different than list1 = list1 + [4, 5, 6]
see:
list1 = [1, 2, 3]
id(list1)
45889616
list1 += [4, 5, 6 ]
id(list1)
45889616 # < -same address
list1
[1, 2, 3, 4, 5, 6]
so list1 += [4, 5, 6 ] updates the existing list
list1 = [1, 2, 3]
id(list1)
45888656
list1 = list1 + [4, 5, 6]
id(list1)
45862424 # <- a new address
list1
[1, 2, 3, 4, 5, 6]
so list1 = list1 + [4, 5, 6] create a new list
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