1. What versions are you using?
   3.1.1
   DB version independent

2. Is it an error or a hang or a crash?
   Error

3. What error(s) or behavior you are seeing?
   DPY-4010 in thin mode, works in thick

4. Does your application call init_oracle_client()?
   It doesn't, but calling it works around the problem

5. Include a runnable Python script that shows the problem.

import oracledb

# oracledb.init_oracle_client() # comment this out and it works                                                                                                                                                                                                                                                                                                                                   
conn = oracledb.connect("...")
cursor = conn.cursor()
cursor.executemany("insert into dual values (:t)", [])

The application builds inputs programmatically, and sometimes they can be missing.
The confusing part is this works in thick mode, when the app was built, but fails now that I migrated to thin