import yaml

def inventory():

  ip_list = {}
  ip_list['10.25.152.200'] = None
  ip_list['10.25.152.201'] = None

  inventory = dict(all = dict (
    children = dict(
      qa = dict(
        hosts = ip_list,
        vars = dict(
            ansible_ssh_user = 'foo',
            ansible_ssh_pass = 'bar'
          )
        )
      )
    )
  )

  return inventory

def main():
  with open('/tmp/inventory.yml', 'w') as outfile:
    yaml.dump(inventory(), outfile, default_flow_style=False)

if __name__ == "__main__":
    main()