How to convert a string representation of an array of objects to an array of objects?

Question

To convert an array of objects to a string, I can use str(arr).
Reversely, is there a built-in Python function to convert a string representation of an array of object to an array of objects?

In other words, how to convert "[{'key1': 'val1', 'key2': 'val2'}]" back to an array of objects? I thought of doing it using split but it wouldn't be clean like str().

// examples
arr = [{'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}, {'key1': 'val1', 'key2': 'val2'}]
arrStr = str(arr)
// "[{'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}, {'key1': 'val1', 'key2': 'val2'}]"

arr2 = [{'key1': 'val1', 'key2': 'val2'}]
arrStr2 = str(arr)
// "[{'key1': 'val1', 'key2': 'val2'}]"

it is not even the same as the linked duplicated question. https://stackoverflow.com/questions/1894269/how-to-convert-string-representation-of-list-to-a-list — Jun, May 02 '21 at 06:23

Daniel Scott · Answer 1 · 2021-05-02T02:07:50.790

-1

import json

array_of_objects = json.loads("[{'key1': 'val1', 'key2': 'val2'}]".replace("'",'"'))

Here's a speed comparison for the concerned parties:

import ast
import json

s = "[{'key1': 'val1', 'key2': 'val2'}]"

def kludge():
    json.loads(s.replace("'",'"'))

def fast():
    ast.literal_eval(s)
    
%timeit kludge()
%timeit fast()
>>> 2.02 µs ± 14.8 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
>>> 10 µs ± 25.6 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

edited May 02 '21 at 02:07

answered May 02 '21 at 01:39

Daniel Scott

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JSON uses double quotes around strings, not single qutoes – Barmar May 02 '21 at 01:40
You're exactly right. And my solution works for op. – Daniel Scott May 02 '21 at 01:42
It won't work if any of the keys or values have single quotes in them, they'll be turned into double quotes. – Barmar May 02 '21 at 01:59
Why use a kludge like this instead of the tool that's built for the job, `ast.literal_eval()`? – Barmar May 02 '21 at 01:59
Good point. Updated my answer. – Daniel Scott May 02 '21 at 02:08
Who cares how fast something runs if it might give the wrong result? – Barmar May 02 '21 at 02:12
Me. And possibly op too. – Daniel Scott May 02 '21 at 02:25
Let's both admit there's tradeoffs. Glad op gets to see both sides of the story. – Daniel Scott May 02 '21 at 02:26
ast wouldn't work for `'[{"a":null,"b":true}]'` but json split would work – Jun May 04 '21 at 00:31
That's true, but in @Barmar 's defence here, your example is not a 'python string representation of an object'. '[{"a":null,"b":true}]' is JSON. If you're using JSON as an input, it's not up for debate which is the best method -- you should use the Json method. But if you have something like '[{"a":None,"b":true}]', then it's up to you to evaluate tradeoffs between ast and json methods. – Daniel Scott May 09 '21 at 22:25

How to convert a string representation of an array of objects to an array of objects?

1 Answers1