Print traceback call stack in Python

Print Python stack traces without raising an exception.

# in /path/to/a/module.py
import traceback
for line in traceback.format_stack():
    print(line.strip())

# or

print('----- start -----')
import traceback; traceback.print_stack()
print('----- end -----')
>>> import qingcloud.iaas
>>> conn = qingcloud.iaas.connect_to_zone('pek2', '123', '456')
>>> conn.describe_instances(limit=1)
----- start -----
  File "<stdin>", line 1, in <module>
  File "qingcloud/iaas/connection.py", line 214, in describe_instances
    return self.send_request(action, body)
  File "qingcloud/iaas/connection.py", line 42, in send_request
    resp = self.send(url, request, verb)
  File "qingcloud/conn/connection.py", line 245, in send
    request.authorize(self)
  File "qingcloud/conn/connection.py", line 156, in authorize
    connection._auth_handler.add_auth(self, **kwargs)
  File "qingcloud/conn/auth.py", line 118, in add_auth
    import traceback; traceback.print_stack()
----- end -----

ref:
https://stackoverflow.com/questions/3925248/print-python-stack-trace-without-exception-being-raised