python string to dict variable

Question

I have a weird scenario where I need to convert the string like "data["data"]["name"][0]" into a dict variable which can be used to modify the dict variable value

so

input. - "data["data"]["name"][0]" and

output - data["data"]["name"][0]

so that I can use it modify the value of the variable.

Things that I have tried are locals() and globals() way of converting string to Variable but they seems to be failing given the string will actually be a complex dict variable.

update1:-

I was trying to get all the keys(path to keys) of a complex nested json and ended up getting that using collections and strings. so each key's path is string "data["data"]["name"][0]" but to modify the complex json I would need to interpret this as variable and assign value.

sample code

var = "data['data']['name'][0]"
data = {"data":{"name":["test","tst2"]}}
print(data['data']['name'][0])
print(var) # this prints the string
print(eval(var)) # this prints the value of string evaluted or like get method
#how to set value using var variable
#means var should be like data['data']['name'][0]

Can you share how you end up having to deal with something like this - it's really weird and probably this is XY problem. — buran
– buran, Commented Jan 9, 2022 at 8:27
Put the top level into a dict variable you manage, rather than trying to add it to the locals or the globals? In most cases, you don't want to let an input file control variables directly in your program... — Jiří Baum
– Jiří Baum, Commented Jan 9, 2022 at 8:28
exec('data["data"]["name"][0] = "NEW DATA"') this works but not sure if it is suitable in your case. — Mahmoud Embaby
– Mahmoud Embaby, Commented Jan 9, 2022 at 8:51
I was trying to get all the keys(path to keys) of a complex nested json and ended up getting that using collections and strings. this is so wrong. first of all why do you need to hardcore the path as collection of strings, second - instead of string like this why not e.g. tuple ('data', 'name', 0) and then iterate over tuple elements to get the value you want. And this is just slightly better than using string - it's still not completely clear what you ultimately try to achieve. — buran
– buran, Commented Jan 9, 2022 at 9:07
I would suggest that you ask completely different question, showing the JSON and explaining exactly what you want to do with it (expected output), instead of asking how to solve a problem you created yourself. This is XY problem. — buran
– buran, Commented Jan 9, 2022 at 9:09

Lenormju · Accepted Answer · 2022-01-10 10:02:17Z

It is not pretty, but it works :

def set_value(d, selector, val):
    """Follow the selector inside `d` to set the value of the last node."""
    if not selector.startswith("data"):
        raise ValueError("the query does not start with 'data'")

    # start parsing the selector
    parts = selector[len("data"):].split("]")
    if parts[-1] != "":
        raise ValueError("the query does not end with a ']'")
    parts.pop()  # remove the last part, we know it's empty
    current_node = d
    for part in parts[:-1]:  # for each part but not the last
        if (part.startswith("['") and part.endswith("'")) or \
                (part.startswith("[\"") and part.endswith("\"")):  # it's a dictionary access
            key_name = part[2:-1]
            current_node = current_node[key_name]
        elif part[1] in ("0", "1", "2", "3", "4", "5", "6", "7", "8", "9"):
            index_val = int(part[1:])
            current_node = current_node[index_val]
        else:
            raise ValueError(f"the query part {part[:-1]!r} is syntactically incorrect")
    # then handle the last part
    last_part = parts[-1]
    if (last_part.startswith("['") and last_part.endswith("'")) or \
            (last_part.startswith("[\"") and last_part.endswith("\"")):  # it's a dictionary access
        key_name = last_part[2:-1]
        current_node[key_name] = val
    elif last_part[1] in ("0", "1", "2", "3", "4", "5", "6", "7", "8", "9"):
        index_val = int(last_part[1:])
        current_node[index_val] = val
    else:
        raise ValueError(f"the query part {last_part!r} is syntactically incorrect")

    return d


data = {"data": {"name": ["test", "tst2"]}}

print(data)  # {'data': {'name': ['test', 'tst2']}}
data = set_value(data, 'data["data"]["name"][0]', 12)
print(data)  # {'data': {'name': [14, 'tst2']}}
data = set_value(data, "data['data']['name'][1]", -4)
print(data)  # {'data': {'name': [12, -4]}}
data = set_value(data, "data['foo']", {'bar': [5, 6]})
print(data)  # {'data': {'name': [12, -4]}, 'foo': {'bar': [5, 6]}}
data = set_value(data, "data['foo']['qux']", 'hh')
print(data)  # {'data': {'name': [12, -4]}, 'foo': {'bar': [5, 6], 'qux': 'hh'}}

Collectives™ on Stack Overflow

python string to dict variable

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related