I have this JSON in a file:
{
"maps": [
{
"id": "blabla",
"iscategorical": "0"
},
{
"id": "blabla",
"iscategorical": "0"
}
],
"masks": [
"id": "valore"
],
"om_points": "value",
"parameters": [
"id": "valore"
]
}
I wrote this script to print all of the JSON data:
import json
from pprint import pprint
with open('data.json') as f:
data = json.load(f)
pprint(data)
This program raises an exception, though:
Traceback (most recent call last):
File "<pyshell#1>", line 5, in <module>
data = json.load(f)
File "/usr/lib/python3.5/json/__init__.py", line 319, in loads
return _default_decoder.decode(s)
File "/usr/lib/python3.5/json/decoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python3.5/json/decoder.py", line 355, in raw_decode
obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 13 column 13 (char 213)
How can I parse the JSON and extract its values?
data = []
with codecs.open('d:\output.txt','rU','utf-8') as f:
for line in f:
data.append(json.loads(line))
Justin Peel's answer is really helpful, but if you are using Python 3 reading JSON should be done like this:
with open('data.json', encoding='utf-8') as data_file:
data = json.loads(data_file.read())
Note: use json.loads
instead of json.load
. In Python 3, json.loads
takes a string parameter. json.load
takes a file-like object parameter. data_file.read()
returns a string object.
To be honest, I don't think it's a problem to load all json data into memory in most cases. I see this in JS, Java, Kotlin, cpp, rust almost every language I use. Consider memory issue like a joke to me :)
On the other hand, I don't think you can parse json without reading all of it.
As a python3 user,
The difference between load
and loads
methods is important especially when you read json data from file.
As stated in the docs:
json.load:
Deserialize fp (a .read()-supporting text file or binary file containing a JSON document) to a Python object using this conversion table.
json.loads:
json.loads: Deserialize s (a str, bytes or bytearray instance containing a JSON document) to a Python object using this conversion table.
json.load method can directly read opened json document since it is able to read binary file.
with open('./recipes.json') as data:
all_recipes = json.load(data)
As a result, your json data available as in a format specified according to this conversion table:
https://docs.python.org/3.7/library/json.html#json-to-py-table
Your data.json
should look like this:
{
"maps":[
{"id":"blabla","iscategorical":"0"},
{"id":"blabla","iscategorical":"0"}
],
"masks":
{"id":"valore"},
"om_points":"value",
"parameters":
{"id":"valore"}
}
Your code should be:
import json
from pprint import pprint
with open('data.json') as data_file:
data = json.load(data_file)
pprint(data)
Note that this only works in Python 2.6 and up, as it depends upon the with
-statement. In Python 2.5 use from __future__ import with_statement
, in Python <= 2.4, see Justin Peel's answer, which this answer is based upon.
You can now also access single values like this:
data["maps"][0]["id"] # will return 'blabla'
data["masks"]["id"] # will return 'valore'
data["om_points"] # will return 'value'
Here you go with modified data.json
file:
{
"maps": [
{
"id": "blabla",
"iscategorical": "0"
},
{
"id": "blabla",
"iscategorical": "0"
}
],
"masks": [{
"id": "valore"
}],
"om_points": "value",
"parameters": [{
"id": "valore"
}]
}
You can call or print data on console by using below lines:
import json
from pprint import pprint
with open('data.json') as data_file:
data_item = json.load(data_file)
pprint(data_item)
Expected output for print(data_item['parameters'][0]['id'])
:
{'maps': [{'id': 'blabla', 'iscategorical': '0'},
{'id': 'blabla', 'iscategorical': '0'}],
'masks': [{'id': 'valore'}],
'om_points': 'value',
'parameters': [{'id': 'valore'}]}
Expected output for print(data_item['parameters'][0]['id'])
:
valore
"Ultra JSON" or simply "ujson" can handle having []
in your JSON file input. If you're reading a JSON input file into your program as a list of JSON elements; such as, [{[{}]}, {}, [], etc...]
ujson can handle any arbitrary order of lists of dictionaries, dictionaries of lists.
You can find ujson in the Python package index and the API is almost identical to Python's built-in json
library.
ujson is also much faster if you're loading larger JSON files. You can see the performance details in comparison to other Python JSON libraries in the same link provided.
If you're using Python3, you can try changing your (connection.json
file) JSON to:
{
"connection1": {
"DSN": "con1",
"UID": "abc",
"PWD": "1234",
"connection_string_python":"test1"
}
,
"connection2": {
"DSN": "con2",
"UID": "def",
"PWD": "1234"
}
}
Then using the following code:
connection_file = open('connection.json', 'r')
conn_string = json.load(connection_file)
conn_string['connection1']['connection_string_python'])
connection_file.close()
>>> test1
There are two types in this parsing.
From a file, you can use the following
import json
json = json.loads(open('/path/to/file.json').read())
value = json['key']
print json['value']
This arcticle explains the full parsing and getting values using two scenarios.Parsing JSON using Python
Source: Stackoverflow.com