how to add same dictionary to a list with modified value

Question

csv={“a”:0}
list_=[]
for i in range(2):
    csv["a"]+=1
    list_.append(csv)
    print(list_,csv)

I am getting output like this: [{'a': 2}, {'a': 2}]

I need to get an output like this [{'a': 1}, {'a': 2}]

score 3 · Accepted Answer · answered Nov 27 '18 at 17:18

3

Because python pass variables to functions as reference and not as value, you need to pass a copy of the original dictionnary to list_.append():

csv={"a":0}
list_=[]
for i in range(2):
    csv["a"]+=1
    list_.append(dict(csv))
print(list_)

answered Nov 27 '18 at 17:18

Cyphall

What's the role of dict() – Jiss Raphel Nov 27 '18 at 17:29
@JissRaphel The difference is explained [here](https://stackoverflow.com/a/19506043/9962106) – Cyphall Nov 27 '18 at 17:36
@JissRaphel Sorry I missread your question. `dict()` create a new dictionnary from the one you pass in parameter. – Cyphall Nov 27 '18 at 19:27

score 2 · Answer 2 · answered Nov 27 '18 at 17:16

2

You can do a list-comprehension:

list_ = [{'a': x} for x in range(1, 3)]
# [{'a': 1}, {'a': 2}]

answered Nov 27 '18 at 17:16

Austin

2 Answers2