Read, Write and Parse JSON using Python

JSON is a lightweight data format for data interchange which can be easily read and written by humans, easily parsed and generated by machines. It is a complete language-independent text format. To work with JSON data, Python has a built-in package called json.

Example:
s = '{"id":01, "name": "Emily", "language": ["C++", "Python"]}'

The syntax of JSON is considered as a subset of the syntax of JavaScript including the following:

• Name/Value pairs: Represents Data, name is followed by ‘:'(colon) and the Name/Value pairs separated by, (comma).
• Curly braces: Holds objects.
• Square brackets: Hold arrays with values separated by, (comma).

Keys/Name must be strings with double quotes and values must be data types amongst the following: 

• String
• Number
• Object (JSON object)
• array
• Boolean
• Null

Example:
 {
   "employee": [

      {
         "id": "01",
         "name": "Amit",
         "department": "Sales"
      },

      {
         "id": "04",
         "name": "sunil",
         "department": "HR"
      }
   ]
}

Parse JSON (Convert from JSON to Python)

json.loads() method can parse a json string and the result will be a Python dictionary.
Syntax:

json.loads(json_string)

Example:

Python3

# Python program to convert JSON to Python


import json

# JSON string
employee ='{"id":"09", "name": "Nitin", "department":"Finance"}'

# Convert string to Python dict
employee_dict = json.loads(employee)
print(employee_dict)

print(employee_dict['name'])

Output:

{'id': '09', 'department': 'Finance', 'name': 'Nitin'}
Nitin

Python read JSON file

json.load() method can read a file which contains a JSON object. Consider a file named employee.json which contains a JSON object.
Syntax:

json.load(file_object)

Example: Let’s suppose the JSON looks like this.

We want to read the content of this file. Below is the implementation.

Python3

# Python program to read
# json file


import json

# Opening JSON file
f = open('data.json',)

# returns JSON object as
# a dictionary
data = json.load(f)

# Iterating through the json
# list
for i in data['emp_details']:
    print(i)

# Closing file
f.close()

Output:

Here, we have used the open() function to read the JSON file. Then, the file is parsed using json.load() method which gives us a dictionary named data.

Convert from Python to JSON

json.dumps() method can convert a Python object into a JSON string. 
Syntax:

json.dumps(dict, indent)

It takes two parameters:

• dictionary – name of dictionary which should be converted to JSON object.
• indent – defines the number of units for indentation

Example:

Python3

# Python program to convert
# Python to JSON


import json

# Data to be written
dictionary ={
  "id": "04",
  "name": "sunil",
  "department": "HR"
}

# Serializing json
json_object = json.dumps(dictionary, indent = 4)
print(json_object)

Output

{
    "id": "04",
    "name": "sunil",
    "department": "HR"
}

Output:

{
    "department": "HR",
    "id": "04",
    "name": "sunil"
}

The following types of Python objects can be converted into JSON strings: 

• dict
• list
• tuple
• string
• int
• float
• True
• False
• None

Python objects and their equivalent conversion to JSON:

Python	JSON Equivalent
dict	object
list, tuple	array
str	string
int, float	number
True	true
False	false
None	null

Writing JSON to a file

json.dump() method can be used for writing to JSON file.
Syntax:

json.dump(dict, file_pointer)

It takes 2 parameters:

• dictionary – name of dictionary which should be converted to JSON object.
• file pointer – pointer of the file opened in write or append mode.

Python3

# Python program to write JSON
# to a file


import json

# Data to be written
dictionary ={
    "name" : "sathiyajith",
    "rollno" : 56,
    "cgpa" : 8.6,
    "phonenumber" : "9976770500"
}

with open("sample.json", "w") as outfile:
    json.dump(dictionary, outfile)

Output:

The above program opens a file named sample.json in writing mode using ‘w’. The file will be created if it does not exist. Json.dump() will transform dictionary to a JSON string and it will be saved in the file sample.json.