from firebird.driver import connect, driver_config
driver_config.fb_client_library.value = r'C:\Program Files (x86)\Firebird\Firebird_2_5\bin\fbclient.dll'
con = connect(r'D:/Bd_dados/DEVSYS_DATABASE.GDB', user='SYSDBA', password='masterkey')
cur = con.cursor()
cur.execute("SELECT RDB$RELATION_NAME FROM RDB$RELATIONS WHERE RDB$SYSTEM_FLAG=0 ORDER BY 1")
for r in cur.fetchall():
    print(r[0].strip())
con.close()