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pythonlistvariable-assignment
callmepeanut
callmepeanut

Reputation: 3

Python：nest list assignment does not work properly

Thr version of Python is 2.6.6

n = 0
list1=["","",""]
list2=[]
for ...    :
    # a b c changes every loop
    list1[0]=a
    list1[1]=b
    list1[2]=c
    list2[n].append(list1)
    n += 1

for j in range(n):
    print list2[j]

The problem is that every item in list2 is the value of the last loop, Why? It seems caused by shallow copy, but i don't kown how to fix it.

Upvotes: 0

Views: 45

Answers (1)

YS-L
YS-L

Reputation: 14738

You need to append a copy of list1:

list2.append(list1[:])

Otherwise, what gets appended is a reference to the same single list.

Upvotes: 3

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