Read From File as Json if File Exists Python

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JSON is a popular information format for interchange, and Python is a highly productive programming language with simple programming syntax. Hence, knowing how to piece of work with JSON data in Python can exist a useful tool in the arsenal of any software programmer or coding engineer. Software engineers targeting Python programming jobs must especially learn how to work with JSON information in Python during their technical interview prep. In this article, we volition learn:

What Is JSON?
Importance and Uses of JSON
JSON in Python
How to Read a JSON File in Python
Example of Reading a JSON File in Python
JSON Object and Python Object
FAQs on Reading JSON File Using Python
Issues on Reading a JSON File Using Python

What Is JSON?

JSON stands for JavaScript Object Notation as JSON's syntax borrows from JavaScript'due south object notation syntax. Information technology is a lightweight information-interchange format used for representing, storing, and transferring structured data based on JavaScript object syntax. JSON exists as a cord and stores JSON objects, which store data in the grade of central-value pairs.

JSON object syntax:

Cardinal-value pairs are separated past a comma (,) and each cardinal and its corresponding value is separated by a colon. The keys themselves are strings, and values can exist of one of the following data types: string, number, JSON object, Null, Boolean, or array. Arrays are enclosed in brackets ( [ , , ] ). A JSON object is written inside braces ( { , , } ), and the value of a key itself can exist a JSON object.

Importance and Uses of JSON

A JSON file is typically used to transmit information betwixt a web application and a server. It is used most commonly by spider web services and APIs and in Ajax Web awarding programming.
Unlike XML, where the tags take to be opened and airtight very often, increasing the XML file size, JSON is a more lightweight choice.
JSON is a language-independent format with format conventions easily comprehensible to most programmers.

All this makes JSON an attractive choice for data interchange, and most mod languages support the generation and parsing of JSON format data. Let united states of america now expect at how JSON works in Python.

JSON in Python

Python has a congenital-in package called json, through which the language supports working with the JSON data format. Hence, to work with JSON in Python, exist it JSON strings or JSON files, we must import this json packet. The json package has a json module, which contains functions for working with the JSON data format. Working with JSON involves making use of the methods in this json module.

In Python, JSON exists equally a cord, and JSON objects can be stored in a file.

Examples of JSON as a cord:

Examples of JSON objects stored in a file:

How to Read a JSON File Using Python

The json module contains methods that help the states read JSON files in Python. Permit us wait at the steps involved in the process:

Importing the Bundle json in Python

The first step in reading a JSON file is importing the json packet so that we tin can utilize methods like load() and loads() in its json module that will help us read the JSON file.

import json

Opening a JSON File in Python

The 2nd footstep involves opening the JSON file, which we can do using the built-in function open(). The format for the open office is:

fileContent= open("X:/filePath/fileName.json")

Annotation the forward-slash (/) instead of backward slash (\) used in the path. We tin can besides utilise a double backward slash (\\). The aim is for the path to read the whole path as a string and not treat something similar \n in 10:\filePath\newfile.json as an escape character. Here, the variable fileContent is of type cord and will store the contents of the JSON file at the given path.

Loading JSON Data From a JSON File in Python

Next, we need to parse the JSON data stored in fileContent and shop information technology equally a Python dictionary. The load() role in the json module does exactly that and returns the JSON object every bit a python dictionary. So the returned dictionary stores the parsed data from the JSON file. The load office is written in the post-obit format:

parsedJsonDictionary = json.load(fileContent)

When we utilize the load() or loads() function, we're converting JSON objects into their respective Python objects. This process is called deserialization of JSON.

If nosotros have JSON data in string format, we can utilise the loads() office, where the additional 's' in loads() stands for the fact that it takes a JSON string as its argument.

parsedJsonDictionary = json.loads(information)

Endmost a JSON File in Python

Since we've got what we demand from the file, nosotros should at present shut it. Nosotros do this using the shut() function in the following format:

fileContent.close()

Reading a JSON File in Python

Nosotros have now successfully read the JSON file. Hence to read a JSON file, the steps involved are:

Opening the file to read
Loading the contents of the file into a Python dictionary
Closing the file

The JSON objects and their cardinal-value pairs are all populated as a Python dictionary and can be accessed and printed the same way you lot would for any Python dictionary. Nosotros'll at present take an example where we read a file and show all these steps as they should occur in order.

Example of Reading a JSON File in Python

# Python program for reading a JSON file

# Imports the JSON package

import json

# Opens the required JSON file

fileContent= open("Ten:/filePath/fileName.json")

# Returns a Python lexicon by deserializing JSON

parsedJsonDictionary = json.load(fileContent)

# Closing file

fileContent.shut()

# Prints the Python dictionary that at present stores the data in JSON file

print(parsedJsonDictionary)

Output:

The output is the contents of the JSON file fileName.json, stored as primal-value pairs into a Python dictionary, just every bit any Python dictionary would be printed.

JSON Object and Python Object

As we've learned, when JSON is deserialized, JSON objects are converted into their equivalent Python objects. Permit us see what that looks like with the help of a table. The table states a JSON object and and so states the Python object it'll be stored every bit after deserialization using load()/loads():

Examples of Problems on Reading JSON File Using Python

Traverse a JSON tree structure (for instance, inorder) and add all its nodes into a list.
Read a JSON file containing non-ASCII characters successfully in Python.

For more tech interview questions and bug, cheque out the following pages: Interview Questions , Issues , Learn

FAQs on Reading a JSON File Using Python

Question 1: What'due south the departure betwixt a Python dictionary and a JSON object?

A Python lexicon is a information structure, while a JSON object is just a pure string written in a structured format. Strings in a Python dictionary utilize single quotes, whereas strings in a JSON object utilise double-quotes. There's also a divergence in key — in a Python dictionary, a key tin can be whatever hash object; in a JSON object, a key has to be a cord. Here's a summary of the differences:

Question 2: What is the difference between load() and loads()?

The office loads() is used if the statement is a JSON string, while load() accepts a JSON file object every bit the argument. In other words, nosotros use loads() to read JSON from a JSON cord, utilize load() to read JSON from a JSON file object.

Question 3: What is the departure between a JSON object and a JSON string?

JSON e'er exists as a cord. What we ofttimes refer to as JSON objects are JavaScript object literals. Information written in JSON format is only truly JSON if it's used in a string context.

This is a JSON string:

data = '{"keyone": "valueone", "keytwo": {"keyA": "valueA", keyB": "valueB"}}'

This is a JSON object, which is really an object literal and not JSON:

dataObject = {"keyone": "valueone", "keytwo": {"keyA": "valueA", keyB": "valueB"}}

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Commodity contributed Tanya Shrivastava

randallpron1974.blogspot.com

Source: https://www.interviewkickstart.com/learn/read-json-file-in-python

Randall Pron1974