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JSON encoding and decoding with Python

Introduction
JSON (JavaScript Object Notation) is frequently used between a server and a web application. An example of JSON data:

{
"persons": [
{
"city": "Seattle",
"name": "Brian"
},
{
"city": "Amsterdam",
"name": "David"
}
]
}

The json module enables you to convert between JSON and Python Objects.

JSON conversion examples


Convert JSON to Python Object (Dict)
To convert JSON to a Python dict use this:

import json

json_data = '{"name": "Brian", "city": "Seattle"}'
python_obj = json.loads(json_data)
print python_obj["name"]
print python_obj["city"]

Convert JSON to Python Object (List)
JSON data can be directly mapped to a Python list.

import json

array = '{"drinks": ["coffee", "tea", "water"]}'
data = json.loads(array)

for element in data['drinks']:
print element

Convert JSON to Python Object (float)
Floating points can be mapped using the decimal library.

import json
from decimal import Decimal

jsondata = '{"number": 1.573937639}'

x = json.loads(jsondata, parse_float=Decimal)
print x['number']

Convert JSON to Python Object (Example)
JSON data often holds multiple objects, an example of how to use that below:

import json

json_input = '{"persons": [{"name": "Brian", "city": "Seattle"}, {"name": "David", "city": "Amsterdam"} ] }'

try:
decoded = json.loads(json_input)

# Access data
for x in decoded['persons']:
print x['name']

except (ValueError, KeyError, TypeError):
print "JSON format error"

Convert Python Object (Dict) to JSON
If you want to convert a Python Object to JSON use the json.dumps() method.

import json
from decimal import Decimal

d = {}
d["Name"] = "Luke"
d["Country"] = "Canada"

print json.dumps(d, ensure_ascii=False)
# result {"Country": "Canada", "Name": "Luke"}

Converting JSON data to Python objects
JSON data can be converted (deserialized) to Pyhon objects using the json.loads() function. A table of the mapping:

JSON Python
object dict
array list
string str
number (int) int
number (real) float
true True
false False
null None

Pretty printing



If you want to display JSON data you can use the json.dumps() function.

import json

json_data = '{"name": "Brian", "city": "Seattle"}'
python_obj = json.loads(json_data)
print json.dumps(python_obj, sort_keys=True, indent=4)

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