[Python] How to fix the error 'DPY-4001: no password specified' of oracledb in python

I am trying to connect oracle DB, using the package 'oracledb'. But I can see the below error that states.

Error

File "C:\Users\userid\Anaconda3\lib\site-packages\oracledb\errors.py", line 103, in _raise_err
raise exc_type(_Error(message)) from cause
oracledb.exceptions.DatabaseError: DPY-4001: no password specified


Note: This is an example code, however, I have already tried with the original configuration details.

The documentation I followed : https://python-oracledb.readthedocs.io/en/latest/user_guide/installation.html

Python version: 3.9.12 Coding through Anaconda(jupyter notebook)

Could someone help me to fix this?

code

import oracledb
import os

un = os.environ.get('PYTHON_USERNAME')
pw = os.environ.get('PYTHON_PASSWORD')
cs = os.environ.get('PYTHON_CONNECTSTRING')

with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
with connection.cursor() as cursor:
sql = """select sysdate from dual"""
for r in cursor.execute(sql):
print(r)

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