Valid JSON won't load using Python JSON module

Question

I have data from openWeather in JSON format which gives the error

Traceback (most recent call last):
  File "testjson.py", line 7, in <module>
    data = json.load(data_file)
  File "E:\Program Files\Python27\lib\json\__init__.py", line 290, in load
    **kw)
  File "E:\Program Files\Python27\lib\json\__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "E:\Program Files\Python27\lib\json\decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "E:\Program Files\Python27\lib\json\decoder.py", line 384, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

I have run the JSON data through JSONlint and it's OK. This is it

{"city":{"id":7839581,"name":"Gold Coast","coord":{"lon":153.36055,"lat":-27.97851},"country":"AU","population":0,"sys":{"population":0}},"cod":"200","message":0.0184,"cnt":40,"list":[{"dt":1488844800,"main":{"temp":297.46,"temp_min":297.12,"temp_max":297.46,"pressure":1019.12,"sea_level":1025.73,"grnd_level":1019.12,"humidity":100,"temp_kf":0.34},"weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01d"}],"clouds":{"all":0},"wind":{"speed":5.16,"deg":203.005},"rain":{}}]}

and lastly my Python code

import json
from pprint import pprint


with open('weather.json') as data_file:    
    data = json.load(data_file)

pprint(data)

I've been messing with this for hours, chasing up leads here and anywhere else the searching takes me. Unlike a lot of more subtle errors, this just seems to be rejecting the whole lot, and I don't know why

Could anyone shed some light on this ?

That string loads using json.loads, so you might want to actually do a s = data_file.read(), then print it out and see that the contents of the weather.json is actually what you think it was. — metatoaster
– metatoaster, Commented Mar 11, 2017 at 1:45
Seems fine. Are you absolutely sure the source file is okay? Have you passed it to a JSON checker or did you just copy paste the plain text? — Denziloe
– Denziloe, Commented Mar 11, 2017 at 1:48
I checked the JSON data with several online tools and the Chrome JSON addon. I also found that the jq utility parses it just fine. But, I also tried doing an s=data_file.read then printing the string: it appears to have 3 unprintable characters at the start of it. They don't show up in a text editor though... — Robert Murphy
– Robert Murphy, Commented Mar 11, 2017 at 2:48

Chiheb Nexus · Accepted Answer · 2017-03-11 02:23:06Z

1

You need to read the data first from your file then load it using json module like this example:

import json

with open("weather.json", 'r') as f:
    # read the data
    data = f.read()
    # then load it using json.loads()
    final = json.loads(data)

print(final['city'])

Output:

{u'name': u'Gold Coast', u'country': u'AU', u'coord': {u'lat': -27.97851, u'lon': 153.36055}, u'sys': {u'population': 0}, u'id': 7839581, u'population': 0}

Edit:

You can also use json.load() to achieve this task like the example below:

import json

with open("weather.json", 'r') as f:
    final = json.load(f)

print(final['city'])

Output:

{u'name': u'Gold Coast', u'country': u'AU', u'coord': {u'lat': -27.97851, u'lon': 153.36055}, u'sys': {u'population': 0}, u'id': 7839581, u'population': 0}

Why this is working like this way ? It's simple, you may have a look at the documentation json.load() the input must have read() method:

Deserialize fp (a .read()-supporting file-like object containing a JSON document) to a Python object using this conversion table.

Otherwise within json.loads() the input must be a str or unicode instance:

Deserialize s (a str or unicode instance containing a JSON document) to a Python object using this conversion table.

PS: If both methods fails, you should take a look at your file and check if it contain a valid JSON or not.

edited Mar 11, 2017 at 2:23

answered Mar 11, 2017 at 1:53

Chiheb Nexus

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3 Comments

Denziloe Over a year ago

I'm confused. I'm probably being slow but the second method you recommended seems to be exactly the method that was failing in the original question.

Chiheb Nexus Over a year ago

Yes. this is why i used in first place json.loads(). Otherwise if it fails again the OP must check his json file. With his current json input both methods should work fine.

Robert Murphy Over a year ago

Yes I have tried opening and reading the file then using loads() on the string I've read, I get the same result. When I print the string, though, i get those odd characters. using read(1) on the file, and using ord() i get 239, 187, 191. That is, creating a string from the contents of the file puts those characters at the start of it. They don't show up in vi, or any other editor I have. So, there may be somehting wrong wiht the json file, but like I said, jq parses it and all the lint checkers online think it's OK

Robert Murphy · Accepted Answer · 2017-03-11 03:22:07Z

0

OK looks like my json was corrupt. reading the first three characters gave them high-ASCII ord values, so I edited the file with a hex editor, it did indeed have 3 characters at the start. How they may have got there is an utter mystery, I have been using ascii editors the whole time. Thanks for the responses; this was really an odd one. I now have an issue that pprint's output isnt really very pretty, but I can now read the file and have a dictionary. Many thanks.

answered Mar 11, 2017 at 3:22

Robert Murphy

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2 Comments

Robert Murphy Over a year ago

Yep that's exactly what it was. I didn't know they existed, nice call. I'd just copy and pasted the json from a browser window, somehow the mark was inserted in the process. Cheers!

Robert Murphy Over a year ago

I am unsure of the protocol regarding this item. The root cause of the problem has nothing to do with Python or with JSON and perhaps makes this item out of scope; it may be however that others will find themselves with the same issue. It is caused by my text editor - Emeditor - and the way it handles encodings. I have never noticed it before as the BOM is invisible. I had used vi as well during work, it didn't show the BOM characters either. There is an option within Emeditor to save without signature, this will fix the issue.

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