Pandas version checks

  • [x] I have checked that this issue has not already been reported.

  • [x] I have confirmed this bug exists on the latest version of pandas.

  • [x] I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
import pytest

sample_json = [
    {
        "customer_id": 1,
        12: 20,
        13: [{"a": [1, 2,3]}, {"a": [4, 5]}],
        14: [{1000: [1, 2,3]}, {1000: [4, 5]}],
        "name": "Alice",
        "purchases": [
            {
                "purchase_id": 301,
                "date": "2024-06-01",
                "waffles": [
                    {"waffle_id": "W1", "type": "Belgian", "flavor": "Vanilla", "quantity": 2},
                    {"waffle_id": "W2", "type": "Chocolate", "flavor": "Chocolate", "quantity": 1}
                ]
            },
            {
                "purchase_id": 302,
                "date": "2024-06-10",
                "waffles": [
                    {"waffle_id": "W3", "type": "Strawberry", "flavor": "Strawberry", "quantity": 3}
                ]
            }
        ]
    }
]

@pytest.mark.parametrize(
    "args",
    [
        pytest.param({}, id="no args (base case)"),
        pytest.param( dict(record_path=[13]), id="int as record path"),
        pytest.param( dict(record_path=[13, "a"]), id="int and str as record path"),
        pytest.param( dict(record_path=[14, 1_000]), id="int + int as record path"),
        pytest.param(dict(meta=[12]), id="int as meta field"),
        pytest.param(dict(meta=[12, 13]), id="int + int as meta field"),
        pytest.param(dict(meta=[12, "name"]), id="int + string as meta fields"),
        pytest.param(dict(meta=["name", 12]), id="int + string as meta fields (2)"),

        pytest.param(dict(record_path=["purchases"], meta=[12]), id="int as meta & record path"),
        pytest.param(dict(record_path=["purchases"], meta=[12, 13]), id="int +int as meta & record path"),
        pytest.param(dict(record_path=["purchases"], meta=[12, "name"]), id="int + string as meta fields & record path"),
        pytest.param(dict(record_path=["purchases"], meta=["name", 12]), id="int + string as meta fields & record path(2)"),

        pytest.param(

    ]
)
def test_normalize_df(args: dict, data: dict = sample_json):
    """"
    Load from nested object into a dataframe
    """
    df = pd.json_normalize(data, **args)

Issue Description

Specifying an integer as a meta field while specifying a record_path results in TypeError.

        meta_vals: DefaultDict = defaultdict(list)
>       meta_keys = [sep.join(val) for val in _meta]
                     ^^^^^^^^^^^^^
E       TypeError: sequence item 0: expected str instance, int found

Details: * This error only happens when the record_path argument is provided. * No error with ints as keys in record_path * Yes error when a single int is passed as meta arg, or when multiple fields are passes (and one of them is an int)

Expected Behavior

pd.json_normalize should use integers as keys in the meta argument.

Installed Versions

>>> import pandas as pd >>> pd.show_versions() INSTALLED VERSIONS ------------------ commit : 4665c10899bc413b639194f6fb8665a5c70f7db5 python : 3.12.7 python-bits : 64 OS : Darwin OS-release : 24.6.0 Version : Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T8132 machine : arm64 processor : arm byteorder : little LC_ALL : None LANG : None LOCALE : None.UTF-8 pandas : 2.3.2 numpy : 2.3.2 pytz : 2025.2 dateutil : 2.9.0.post0 pip : None Cython : None sphinx : None IPython : None adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : None blosc : None bottleneck : None dataframe-api-compat : None fastparquet : None fsspec : None html5lib : None hypothesis : None gcsfs : None jinja2 : None lxml.etree : None matplotlib : None numba : None numexpr : None odfpy : None openpyxl : None pandas_gbq : None psycopg2 : None pymysql : None pyarrow : None pyreadstat : None pytest : 8.4.2 python-calamine : None pyxlsb : None s3fs : None scipy : None sqlalchemy : None tables : None tabulate : None xarray : None xlrd : None xlsxwriter : None zstandard : None tzdata : 2025.2 qtpy : None pyqt5 : None