Appending instanse attribute as list in for loop

I’ve written a simplified example of the logic of the class, which I find confusing.

class Result:

    def __init__(self):
        self.limit = 10
        self.params_with_error = []

    def get_result(self, offset_range):
        qs = {'limit': self.limit}
        for chunk in range(offset_range):
            print(f'chunk: {chunk}')
            print(f'__Params_with_error__: {self.params_with_error}')

            qs.update({'offset': chunk * self.limit})

            if chunk in (5, 7):
                print('IF condition')
                self.params_with_error.append(qs)
        print(f'Result param: {self.params_with_error}')

result = Result()
result.get_result(10)

And this code return

chunk: 0
__Params_with_error__: []
chunk: 1
__Params_with_error__: []
chunk: 2
__Params_with_error__: []
chunk: 3
__Params_with_error__: []
chunk: 4
__Params_with_error__: []
chunk: 5
__Params_with_error__: []
IF condition
chunk: 6
__Params_with_error__: [{'limit': 10, 'offset': 50}]
chunk: 7
__Params_with_error__: [{'limit': 10, 'offset': 60}]
IF condition
chunk: 8
__Params_with_error__: [{'limit': 10, 'offset': 70}, {'limit': 10, 'offset': 70}]
chunk: 9
__Params_with_error__: [{'limit': 10, 'offset': 80}, {'limit': 10, 'offset': 80}]
Result param: [{'limit': 10, 'offset': 90}, {'limit': 10, 'offset': 90}]

And I don’t understand at all how such a result can come about.
I expect that if the if condition occurs twice, the final result is equivalent to

[{'limit': 10, 'offset': 50}, {'limit': 10, 'offset': 70}]

Why does self.params_with_error continue to change further in the loop? I also don’t understand why the final value of Result param: [{'limit': 10, 'offset': 90}, {'limit': 10, 'offset': 90}]
How do I get the results I want?

>Solution :

dictionaries are mutable, you only created 1 dictionary in your entire code snippet.

qs = {'limit': self.limit}

everything else in the code just references or updates this dictionary, so your final result just has 2 references to the same dictionary, it was never copied.

self.params_with_error = [qs, qs]

to get the result you want, just append a copy of your dictionary not a reference to it.

import copy

self.params_with_error.append(copy.copy(qs))