MicroPython Forum (Archive)

Hello,

I have a dictionnary that I want to copy into another to later check if any change was done in the first one. However dict.deepcopy() is not recognised and dict1 = dict(dict2) has the same effect as dict1 = dict2. Does anyone know a way around this ?

You can use copy() to create a shallow copy (tested on the unix version of micropython). There is a deepcopy implementation found in the copy module in micropython-lib:
https://github.com/micropython/micropyt ... py/copy.py

I'm sorry I wasn't precise enough, I have a dictionnary inside a dictionnary, like that : And in this case, if I do b = a.copy, and then change a, it changes b. But as I only have one entry in the first dictionnary, I can just do

So you want deepcopy.

Indeed. To me @dhylands resolved this query, unless I'm failing to grasp the problem.

in python I would do:
[code] from copy import deepcopy
dict2 = deepcopy(dict1) [/code]
see: https://stackoverflow.com/questions/2465921/how-to-copy-a-dictionary-and-only-edit-the-copy

when I try this in micropython I get
[code]ImportError: no module named 'copy'[/code]

so what is the micropython way of doing this?

marcwagner wrote: ↑

Wed Sep 19, 2018 6:04 pm

in python I would do:

Code: Select all

from copy import deepcopy
dict2 = deepcopy(dict1)

see: https://stackoverflow.com/questions/246 ... t-the-copy

when I try this in micropython I get

Code: Select all

ImportError: no module named 'copy'

so what is the micropython way of doing this?

You have to add this .py file to micropython

https://github.com/micropython/micropyt ... py/copy.py

because deepcopy is not builtin.

Based on your dict in a dict example it appears you are using only immutable objects (strings and integers), dicts, and lists in the thing you want to copy. If that is the case it would be much more efficient to do a json.dumps() followed immediately by a json.loads(). The deepcopy function has a lot of extra code that makes it inefficient for simple collections like those that can be represented by a JSON string. An additional bonus is that the json module is included in micropython by default.