BUG: pd.json_normalize() does not handle index while working with Series

[tommasogallingani]

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

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

• (optional) I have confirmed this bug exists on the master branch of pandas.

---

Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.

Code Sample, a copy-pastable example

pd.json_normalize(test_data['mycol'])
import pandas as pd
test_data =  pd.DataFrame([[{'a':1,'b':4,'c':0}],[ {'a':10,'b':10,'c':10}],[{'a':0,'b':0,'c':0}]], index=[5,2,3], columns=['mycol'])
pd.json_normalize(test_data['mycol'])

	a	b	c
0	1	4	0
1	10	10	10
2	0	0	0

Problem description

When a Series is passed to json_normalize the function returns a re-indexed dataframe without taking into account the index passed through the Series. This beahaviour is absolutely unexpected while working with Series

Expected Output

	a	b	c
5	1	4	0
2	10	10	10
3	0	0	0

Output of pd.show_versions()

INSTALLED VERSIONS

commit : 3e89b4c
python : 3.8.5.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19041
machine : AMD64
processor : Intel64 Family 6 Model 158 Stepping 10, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : Italian_Italy.1252

pandas : 1.2.0
numpy : 1.19.5
pytz : 2021.1
dateutil : 2.8.2
pip : 20.3.3
setuptools : 51.1.2.post20210112
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : 2.8.6 (dt dec pq3 ext lo64)
jinja2 : 3.0.1
IPython : 7.26.0
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : 0.8.5
fastparquet : None
gcsfs : None
matplotlib : 3.3.3
numexpr : None
odfpy : None
openpyxl : 3.0.6
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : 0.5.2
scipy : 1.6.0
sqlalchemy : 1.3.22
tables : None
tabulate : None
xarray : None
xlrd : 1.2.0
xlwt : None
numba : None

[phofl]

data is supposed to be a list or a dict, not a Series. So this is expected.

on a related note: I am not able to find the docs after 1.2.5, can anybody double check please?

[asishm]

on a related note: I am not able to find the docs after 1.2.5, can anybody double check please?

possibly xref #42540

[phofl]

Should have checked, thx

[mroeschke]

Closing as the expected behavior