python - Create new list in for loop -


this question has answer here:

i'm trying create new list changing other in loop, using append method. have trouble it.

my simple code:

l1=[] l2=[0,0] in range(4):     l2[0]+=1     l1.append(l2)     print l2 print l1

return:

[1, 0] [2, 0] [3, 0] [4, 0] [[4, 0], [4, 0], [4, 0], [4, 0]]

but expected list l1 this: [[1,0], [2,0], [3,0], [4,0]] made mistake?

you appending reference list. , since, @ end of loop, value of l2 [4,0], each list inside l1 [4,0]

you can append copy of list of list() built-in method or, using slicing notation shown below

l1=[] l2=[0,0] in range(4):     l2[0]+=1     l1.append(list(l2)) # or l1.append(l2[:])     print l2 print l1

if not able understand idea, can use viz mode of codeskulptor , run code line line, understand properly.


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