Insert element in list python

Question

Why this code:

result_list = [[]]*14
result_list[3].append('sdfda')
print(result_list)

is output:

[['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda'], ['sdfda']]

but i expect:

[[], [], [], ['sdfda'], [], [], [], [], [], [], [], [], [], []]

I want to insert elements by index...but this example of code insert the element in all list of list

In short, in the line `result_list = [[]]*14`, you create 14 "references" to the same empty list, meaning that when you `append` to one, you append to all of them. — dspencer, Apr 02 '20 at 10:28

score 0 · Answer 1 · answered Apr 02 '20 at 10:31

When you write [x]*3 you get, essentially, the list [x, x, x]. That is, a list with 3 references to the same x. When you then modify this single x it is visible via all three references to it.

Try this:

result_list = [[]]*14
result_list[3]=['sdfda']
print(result_list)

Insert element in list python

1 Answers1