Some questions about the "append" function in Python

Question

i've met a problem when using the append function of python. if i code like this:

a={}
a[1]=[1]
b=copy(a)
b[1].append(2)
print (a)

the result will be:

{1: [1, 2]}

why? i think that using the copy function, the address of anything related to b will not influence a. but this append function is really strange! could anyone please tell me how this works? how could i append something without influencing the original address? thanks a lot!

You need to make a deepcopy of a. – Will_of_fire Aug 25 '17 at 03:23 — Will_of_fire, Aug 25 '17 at 03:23

score 0 · Answer 1 · answered Aug 25 '17 at 03:13

0

copy only does a shallow copy. The list element a[1] is still copied by reference.

answered Aug 25 '17 at 03:13

Avery235

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thx a lot. i changed the copy into deepcopy, and it works! – R.Yan Aug 25 '17 at 03:17

Some questions about the "append" function in Python

1 Answers1