Iterate over nested dictionary and replacing the keys in Python

Question

I'm trying to replace all spaces in the dictionary's keys with "_" the code is:

test_parameters = {
        'Debug Properties': {'DUT WRT Dump': True, 'DUT WRT Tool': True, "DUT Preset": "Stater"},
        'Attenuation Values': {'DUT To BTOE': '3'},
        'BT Parameters': {'Connection Interval': '7.5', 'Traffic_Duration': '30'},
    }

for group in test_parameters:
    new_group_name = group.replace(" ", "_")
    group_value = test_parameters.pop(group)
    test_parameters.update({new_group_name: group_value})
    for key in test_parameters[new_group_name]:
        new_key_name = key.replace(" ", "_")
        key_value = test_parameters[new_group_name].pop(key)
        test_parameters[new_group_name].update({new_key_name: key_value})

the first nested dictionary 'Debug Properties' working fine, then when the code finish the last code line for 'DUT To BTOE' the for is failing with error "RuntimeError: dictionary keys changed during iteration"

how can I achieve this functionality?

Thanks

You need to make a new dictionary, you can't modify the dictionary you're iterating over. — Barmar, Apr 28 '23 at 16:13

S.B · Accepted Answer · 2023-04-28T16:22:07.257

One way is to create a new dictionary with the desired keys.

To be more flexible with the depth level, do it with a recursive approach:

from pprint import pprint
from typing import Any

test_parameters = {
    "Debug Properties": {
        "DUT WRT Dump": True,
        "DUT WRT Tool": True,
        "DUT Preset": "Stater",
    },
    "Attenuation Values": {"DUT To BTOE": "3"},
    "BT Parameters": {"Connection Interval": "7.5", "Traffic_Duration": "30"},
}

def replace_nested(d: dict[str, Any]):
    return {
        k.replace(" ", "_"): replace_nested(v) if isinstance(v, dict) else v
        for k, v in d.items()
    }

pprint(replace_nested(test_parameters), sort_dicts=False)

output:

{'Debug_Properties': {'DUT_WRT_Dump': True,
                      'DUT_WRT_Tool': True,
                      'DUT_Preset': 'Stater'},
 'Attenuation_Values': {'DUT_To_BTOE': '3'},
 'BT_Parameters': {'Connection_Interval': '7.5', 'Traffic_Duration': '30'}}

Iterate over nested dictionary and replacing the keys in Python

1 Answers1