ModuleNotFoundError: No module named 'pandas' (ubuntu)

Am a new user on ubuntu version 20.04.

The fresh install comes with python 3.8, so i upgrade to latest 3.11.

I do the usual pip install pandas.
Note i also try pip3 install pandas for good measure.

create a test file (called test_pandas.py) which contains this:

import pandas as pd

d = {'a':[1,2,3], 'b':[4,6,8]}
df = pd.Dataframe(d)
print(df)

run file with:

python test_pandas.py

get this error message:

ModuleNotFoundError: No module named 'pandas'

so i run file with this (the for 3.8 version python):

python3 test_pandas.py

and get this:

AttributeError: module 'pandas' has no attribute 'Dataframe'

I have looked in several places (finally this: https://pip.pypa.io/en/stable/installation/), but all fail.

totally lost as what to do.
just want 3.11 (latest version) with a corresponding working pip.

how can i achieve this ?