Python objects and JSON

Question

I have a python object which I dump to json and write to a file.

results = [
{'destination': (x,y), 'id': 'dsss', 'origin': (x,r), 'waypoints': [[s,l],[d,s]]},
{'destination': (x1, y1), 'id': 'ddsdsee', 'origin': (z,f), 'waypoints': [[e,y],[d,e]]}]

with gzip.open("test.json.gz",'w') as outfile:
    json.dump(results,outfile,indent=2)

I then open the file elsewhere, via:

schedule_f = gzip.open("test.json.gz")
schedule = json.load(schedule_f)

pprint(schedule[0]) return:

{'destination': [x,y], 'id': 'dsss', 'origin': [x,r], 'waypoints': [[s,l],[d,s]]

Why are origin and destination fields converted to a list? I clearly specified ( and not [

Your input is not valid Python, the first item in results is missing a closing }. — user6999902
– user6999902, Commented Dec 5, 2016 at 9:02

Daniel Roseman · Accepted Answer · 2016-12-05 08:58:26Z

1

JSON doesn't have any concept of tuples: only arrays, which map to Python lists.

There is no difference from a practical point of view, but if you think you really really need tuples, you will have to convert them yourself

answered Dec 5, 2016 at 8:58

Daniel Roseman

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jlandercy · Accepted Answer · 2016-12-05 08:58:08Z

1

Nested Python objects can be complexer than you are are allowed to store in JSON format. JSON format does only have a container and its parsed as list when you import it into Python.

Such format conversion are not conservative, they destroy informations. You will not be able to store datetime too, it will be casted to string.

answered Dec 5, 2016 at 8:58

jlandercy

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Ignacio Vazquez-Abrams · Accepted Answer · 2016-12-05 08:58:18Z

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JSON does not support tuples, so the json module converts them to arrays, which are supported by JSON.

answered Dec 5, 2016 at 8:58

Ignacio Vazquez-Abrams

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Remi Smirra · Accepted Answer · 2016-12-05 09:00:25Z

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JSON does not know the "(" (it is not specified in the JSON notation).

Your json.dump intelligently converts it to a list.

answered Dec 5, 2016 at 9:00

Remi Smirra

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Fomalhaut · Accepted Answer · 2016-12-05 09:08:30Z

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Please, read what JSON is: https://en.wikipedia.org/wiki/JSON

JSON doesn't support tuple datatype. It supports list only, that's why Python tuples were converted into JSON lists.

answered Dec 5, 2016 at 9:08

Fomalhaut

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AnkurJat · Accepted Answer · 2016-12-05 11:06:15Z

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If you want the dump and load object exactly same then use pickle module instead of json module.

answered Dec 5, 2016 at 11:06

AnkurJat

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