Error while trying to load a JSON object with python 3

Question

I have the following json object I am trying to parse with python 3:

customerData = {   
 "Joe": {"visits": 1},  
 "Carol":  {"visits": 2},  
 "Howard": {"visits": 3},  
 "Carrie": {"visits": 4}  
}

I am using the following python code to parse the object:

import json 

def greetCustomer(customerData):
    response = json.loads(customerData)

I'm getting the following error:

TypeError: the JSON object must be str, bytes or bytearray, not 'dict'

That's not a JSON object; it's a fragment of Python code. customerData is already a dict, which is what you would be using json.loads to produce. — chepner
– chepner, Commented Mar 20, 2018 at 13:21
Do you mean you're trying to turn it into a JSON string? Then you need to go in the other direction: json.dumps() — glibdud
– glibdud, Commented Mar 20, 2018 at 13:21
@chepner Are you saying that I can use the data as is? Just treat it as I would a python dict? — ChrisJ
– ChrisJ, Commented Mar 20, 2018 at 13:28
Yes, because it is a Python dict, which is what the error message is telling you. JSON is just a language-independent string encoding of common data structures. The fact that the syntax is very similar to native Python syntax can be a source of confusion. (See the end of my answer for examples of things that are valid Python but not valid JSON and vice versa.) — chepner
– chepner, Commented Mar 20, 2018 at 13:34

ted · Accepted Answer · 2019-07-17 22:02:36Z

15

You seem to be mistaking load and dump.

json.loads converts a string to a python object, json.load converts a json file into a python object whereas json.dumps converts a python object to a string and json.dump writes a json string to a file from a python object

Tip: notice that loads and dumps have an s at the end, as in string

edited Jul 17, 2019 at 22:02

answered Mar 20, 2018 at 13:24

ted

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chepner · Accepted Answer · 2018-03-20 13:59:35Z

customerData = {   
 "Joe": {"visits": 1},  
 "Carol":  {"visits": 2},  
 "Howard": {"visits": 3},  
 "Carrie": {"visits": 4}  
}

is Python code that defines a dictionary. If you had

customerJSON = """{   
 "Joe": {"visits": 1},  
 "Carol":  {"visits": 2},  
 "Howard": {"visits": 3},  
 "Carrie": {"visits": 4}  
}"""

you would have a string that contains a JSON object to be parsed. (Yes, there is a lot of overlap between Python syntax and JSON syntax.

assert customerData == json.loads(customerJSON)

would pass.)

Note, though, that not all valid Python resembles valid JSON.

Here are three different JSON strings that encode the same object:

json_strs = [
 "{'foo': 'bar'}",  # invalid JSON, uses single quotes
 '{"foo": "bar"}',  # valid JSON, uses double quotes
 '{foo: "bar"}'     # valid JSON, quotes around key can be omitted
]

You can observe that all(json.loads(x) == {'foo': 'bar'} for x in json_strs) is true, since all three strings encode the same Python dict.

Conversely, we can define three Python dicts, the first two of which are identical.

json_str = json_strs[0]  # Just to pick one
foo = ...  # Some value
dicts = [
  {'foo': 'bar'},     # valid Python dict
  {"foo": "bar"},     # valid Python dict
  {foo: "bar"}        # valid Python dict *if* foo is a hashable value
                      # and not necessarily 
]

It is true that dicts[0] == dicts[1] == json.loads(json_str). However, dicts[2] == json.loads(json_str) is only true if foo == "foo".

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