Parsing JSON

Python includes several built in methods for handling JSON (or json). As you remember from Lesson 1, json is widely used to transfer data from one language to another or from one data source to another. We already looked at some geojson earlier in the lesson when we extracted data from KML's. For this section we will demonstrate loading it into a Python Dictionary and dumping it to a json string.  The official documentation can be found here.

Loading json means to convert a formatted string into a json object. This is useful for converting string representations of dictionaries that come from various sources, or from API’s results. It is important to note that there is also json.load(…) which takes an file or bytes like object as an input parameter whereas json.loads(…) takes a json string. The s at the end of loads denotes that the method is for a string input, whereas the load method without the s is for objects such as files. The dump and dumps follows the same convetion, except it outputs to a file writer type object or a json string so beware of what type of data you are working with. If you do forget, the Python interpreter will kindly let you know.

A simple json loads example: 

import json 
 
# JSON string:Multi-line string 
x = '{"City": "Cheyenne", "State": "Wyoming", "population": "Very Little", "Industries":["Mining", "Restaurants", "Rodeos"]}' 
 
# parse x: 
y = json.loads(x) 
 
print(type(y)) 
print(y) 

To write the python dictionary back to a json string, you would use the .dumps() method.

And a simple json dumps example:

# Creating a dictionary 
wyo_hi_dict = {1:'Welcome', 2:'to', 3:'Cheyenne', 4:'Wyoming'} 
 
# Converts input dictionary into 
# string and stores it in json_string 
json_string = json.dumps(wyo_hi_dict) 

print('Equivalent json string of input dictionary:', json_string) 

Equivalent json string of input dictionary: '{"1": "Welcome", "2": "to", "3": "Cheyenne", "4": "Wyoming"}'

You will notice that the JSON dumps converts the keys and values to strings. The deserialization process converts the value to its datatype, but it doesn't always get it right so sometimes we are left with adding custom casting.

Accessing the properties of the json object when loaded from json.loads() is the same as accessing them via Python dictionary.

print(json_string["1"])