1. What versions are you using?

platform.platform: Darwin-20.6.0-x86_64-i386-64bit

sys.maxsize > 2**32: True

platform.python_version: 3.7.13

oracledb.version: 1.0.1

Database Version: 12.1.0.2.0

2. Is it an error or a hang or a crash?
   Crash (error)
3. What error(s) or behavior you are seeing?

#test-2.py

import oracledb
import os

un = os.environ.get('USER_NAME')
pw = os.environ.get('PASSWORD')
cs = os.environ.get('CONNECT_STRING')
oracledb.init_oracle_client()
with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
   with connection.cursor() as cursor:
      sql = """select version
               from   v$instance"""
      for r in cursor.execute(sql):
         print(r)

python test-2.py
('12.1.0.2.0',)

#test-2.py

import oracledb
import os

un = os.environ.get('USER_NAME')
pw = os.environ.get('PASSWORD')
cs = os.environ.get('CONNECT_STRING')
#oracledb.init_oracle_client()
with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
   with connection.cursor() as cursor:
      sql = """select version
               from   v$instance"""
      for r in cursor.execute(sql):
         print(r)

python test-2.py
Traceback (most recent call last):
File "test-2.py", line 10, in
with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
File "/Users/asrajag/miniconda3/envs/oracle/lib/python3.7/site-packages/oracledb/connection.py", line 1000, in connect
return conn_class(dsn=dsn, pool=pool, params=params, **kwargs)
File "/Users/asrajag/miniconda3/envs/oracle/lib/python3.7/site-packages/oracledb/connection.py", line 128, in init
impl.connect(params_impl)
File "src/oracledb/impl/thin/connection.pyx", line 345, in oracledb.thin_impl.ThinConnImpl.connect
File "src/oracledb/impl/thin/connection.pyx", line 163, in oracledb.thin_impl.ThinConnImpl._connect_with_params
File "src/oracledb/impl/thin/connection.pyx", line 129, in oracledb.thin_impl.ThinConnImpl._connect_with_description
File "src/oracledb/impl/thin/connection.pyx", line 250, in oracledb.thin_impl.ThinConnImpl._connect_with_address
File "src/oracledb/impl/thin/protocol.pyx", line 205, in oracledb.thin_impl.Protocol._connect_phase_two
File "src/oracledb/impl/thin/protocol.pyx", line 296, in oracledb.thin_impl.Protocol._process_message
oracledb.exceptions.DatabaseError: ORA-01017: invalid username/password; logon denied

4. Does your application call init_oracle_client()?

Thick mode works, thin mode does not.
5. Include a runnable Python script that shows the problem.

#test-2.py

import oracledb
import os

un = os.environ.get('USER_NAME')
pw = os.environ.get('PASSWORD')
cs = os.environ.get('CONNECT_STRING')
#oracledb.init_oracle_client()
with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
   with connection.cursor() as cursor:
      sql = """select version
               from   v$instance"""
      for r in cursor.execute(sql):
         print(r)