Better way of merging two json strings in Python for ansible callback_plugin

Question

I'm writing an plugin to return log results as a json file for ansible-playbook.

I'm not super familiar with python, but I've hacked something together that seems to work:

def json_log(res, host):
    if type(res) == type(dict()):
        if 'verbose_override' not in res:
          host_json = JSONEncoder().encode({'host':host})
          result_json = JSONEncoder().encode(res)
          combined_json = host_json + result_json
          combined_json = combined_json.replace("}{", ',')
          print(combined_json)

host_json would be something like: {"host": "centos65"}

result_json would be something like: {"cmd": "echo \"Hello World\" ", "end": "2014-08-01 19:32:38.714584", "stdout": "Hello World", "changed": true, "start": "2014-08-01 19:32:38.707510", "delta": "0:00:00.007074", "stderr": "", "rc": 0, "invocation": {"module_name": "shell", "module_args": "echo \"Hello World\""}}

So I've gone for the brute-force route and just combined the strings and removed the }{ it gets where they join, so it will be in the format I want as valid json:

{"host": "centos65","cmd": "echo \"Hello World\" ", "end": "2014-08-01 19:32:38.714584", "stdout": "Hello World", "changed": true, "start": "2014-08-01 19:32:38.707510", "delta": "0:00:00.007074", "stderr": "", "rc": 0, "invocation": {"module_name": "shell", "module_args": "echo \"Hello World\""}}

So right now I'm just mashing together the two strings and then replacing the join with a comma, is there a smarter way to combine them with the host part being at the start of the json?

Answer 1

res = {"cmd": "echo \"Hello World\" ", "end": "2014-08-01 19:32:38.714584", "stdout": "Hello World", "changed": True, "start": "2014-08-01 19:32:38.707510", "delta": "0:00:00.007074", "stderr": "", "rc": 0, "invocation": {"module_name": "shell", "module_args": "echo \"Hello World\""}}

def json_log(res, host):
    if isinstance(res,dict) and 'verbose_override' not in res:  
           res.update({"host": host})        
           combined_json  = JSONEncoder().encode(res)
           print(combined_json)

In [73]: json_log(res,"centos")
{"cmd": "echo \"Hello World\" ", "end": "2014-08-01 19:32:38.714584", "stdout": "Hello World", "changed": true, "rc": 0, "start": "2014-08-01 19:32:38.707510", "host": "centos", "stderr": "", "delta": "0:00:00.007074", "invocation": {"module_name": "shell", "module_args": "echo \"Hello World\""}}

You can update a dict with the contents of another, the only issue you would ever have is if you had duplicate keys and did not want the values overwritten.

Answer 2

Since they are both dictionaries, you can update one of the two dictionaries with the other one. Ex:

>>> a = {"host": "centos65"}

>>> b = {"cmd": "echo \"Hello World\" ", "end": "2014-08-01 19:32:38.714584", "stdout": "Hello World", "changed": True, "start": "2014-08-01 19:32:38.707510", "delta": "0:00:00.007074", "stderr": "", "rc": 0, "invocation": {"module_name": "shell", "module_args": "echo \"Hello World\""}}

>>> a.update(b)
>>> a
{'cmd': 'echo "Hello World" ', 'end': '2014-08-01 19:32:38.714584', 'stdout': 'Hello World', 'changed': True, 'rc': 0, 'start': '2014-08-01 19:32:38.707510', 'host': 'centos65', 'stderr': '', 'delta': '0:00:00.007074', 'invocation': {'module_name': 'shell', 'module_args': 'echo "Hello World"'}}
>>> a["host"]
'centos65'
>>> a["cmd"]
'echo "Hello World" '
>>>