Python: storing dict inside list

Question

I would like to store the multiple dict inside the list. dict has the same key.

>>> m = {}

>>> l = [] 

>>> for i in range(4):                                                                                                                                                  
...     m["i"] = i+2                                                                                                                                                    
...     m["j"] = i+5                                                                                                                                                    
...     l.append(m)                                                                                                                                                     
...                                                                                                                                                                     
>>> print(l)                                                                                                                                                            
[{'i': 5, 'j': 8}, {'i': 5, 'j': 8}, {'i': 5, 'j': 8}, {'i': 5, 'j': 8}] 

But, I want to know store as below 

[{'i': 2, 'j': 5}, {'i': 3, 'j': 6}, {'i': 4, 'j': 7}, {'i': 5, 'j': 8}]

This is absolutely possible in python. Please provide a [mcve] for your issue, with a _specific_ description of the problem, and the _code_ for what you've tried so far — G. Anderson, Nov 21 '19 at 19:12
Move `m = {}` to the first line after you enter the for loop. — Tony Tuttle, Nov 21 '19 at 19:13
The marked duplicate deals with lists; you have the same trouble with dictionaries, also mutable. You appended four copies of the same object to your list. — Prune, Nov 21 '19 at 19:18

nonamer92 · Accepted Answer · 2019-11-21T19:14:01.923

1

l = []

for i in range(4):
    l.append({'i': i+2, 'j': i+5})

print(l)

outputs:

[{'i': 2, 'j': 5}, {'i': 3, 'j': 6}, {'i': 4, 'j': 7}, {'i': 5, 'j': 8}]

The problem in your code is that m["i"] and m["j"] points to the same memory address on each iteration, and thats why you get all the elements to have the same value in l

edited Nov 21 '19 at 19:14

answered Nov 21 '19 at 19:13

nonamer92

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You can remove the `m = {}` completely as well. – Dave Costa Nov 21 '19 at 19:13

score 0 · Answer 2 · answered Nov 21 '19 at 19:12

0

You should create a new empty dictionary in each iteration of the loop. In your current version, m points to the same object throughout the entire execution, so the list simply contains 4 references to that object.

answered Nov 21 '19 at 19:12

Dave Costa

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Python: storing dict inside list

2 Answers2