JSON_FIles-Py (2).pptx

What is JSON ?
• JSON (JavaScript Object Notation) is a popular data format used for representing structured data. It's common to
transmit and receive data between a server and web application in JSON format.
• JSON was inspired by the JavaScript programming language, but it's not tied to only one language.
• Most modern programming languages have libraries for parsing and generating JSON data.

Why do we use JSON ?
• JSON has a more compact style than XML which was the format of
choice years ago. The light-weight approach can make significant
improvements.
• The XML software parsing process can take a long time. JSON uses
less data overall, so you reduce the cost and increase the parsing
speed.
• The JSON structure is straight forward and often more readable.

Basic JSON syntax
• In JSON, data is written in key-value pairs, like so:
"first_name": "Katie"
• Data is enclosed in double quotation marks and the key-value pair is separated
by a colon.
• There can be more than one key-value pair and each one is separated by a
comma:
"first_name": "Katie", "last_name": "Rodgers“
The example above showed an object, a collection of multiple key-value pairs.
Objects are inside curly braces:
{
"first_name": "Katie",
"last_name": "Rodgers"
}

Another example of JSON-formatted data is as follows:
{
"name": "Frank",
"age": 39,
"isEmployed": true
}

We can also create arrays, an ordered list of values, with JSON. In that
case, arrays are contained inside square brackets:
[
{
},
{
"first_name": "Naomi",
"last_name": "Green"
},
]

// or:
{
"employee": [
{
},
{
"first_name": "Naomi",
"last_name": "Green"
},
]
}
//this created an 'employee' object that has 2 records.
// It defines the first name and last name of an employee

In Python, JSON exists as a string. For example:
p = '{"name": "Bob", "languages": ["Python", "Java"]}'
It's also common to store a JSON object in a file.

Python and JSON
• Python makes it simple to work with JSON files.
• Python supports JSON through a built-in package called JSON.
• To use this feature, we import the JSON package in Python script. in order to use this
module is to import it:
import json
• This library mainly parses JSON from files or strings. It also parses JSON into a
dictionary or list in Python and vice versa, that is converting a Python dictionary or
list into JSON strings.
• The text in JSON is done through quoted-string which contains the value in key-
value mapping within { }.
• It is similar to the dictionary in Python.

JSON to Python (Decoding)
• JSON string decoding is done with the help of method
json.loads() & json.load() of JSON library in Python.
• Reading JSON means converting JSON into a Python value (object).
The json library parses JSON into a dictionary or list in Python.

JSON to Python
• Example 1: Python JSON to dict
• we use the loads() function (load from a string) to parse a JSON string and
the method returns a dictionary.
Here, jsonData is a JSON string, and jsonToPython is a dictionary.

• That is, the data is returned as a Python dictionary (JSON
object data structure).
• So, the statement print jsonToPython[‘name’] returns ‘Frank’
Note: In the above programs, the objects in JSON are converted to dictionaries in Python.

Decoding JSON File or Parsing JSON file in Python(Reading
JSON from a file using Python)
Let us see how to read JSON file in Python with Python parse JSON
example:
NOTE: Decoding JSON file is File Input /Output (I/O) related operation. The
JSON file must exist on your system at specified the location that you
program.
• Deserialization is the opposite of Serialization, i.e. conversion of JSON objects
into their respective Python objects. The load() method is used for it.
• If you have used JSON data from another program or obtained it as a string
format of JSON, then it can easily be deserialized with load(), which is usually
used to load from a string, otherwise, the root object is in a list or Dict

Example 1 : Python read JSON file
You can use json.load() method to read a file containing JSON object.
Suppose, you have a file named person.json which contains a JSON object.
{"name": "Bob",
"languages": ["English", "French"]
}
Here's how you can parse this file:
import json
with open('path_to_file/person.json', 'r') as f:
data = json.load(f)
print(data)
# Output: {'name': 'Bob', 'languages': ['English', 'French’]}
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.

Example 1 : Python read JSON file
import json
#File I/O Open function for read data from JSON File
with open('X:/json_file.json') as file_object:
# store file data in object
data = json.load(file_object)
print(data)
Here data is a dictionary object of Python as shown in the above read JSON
file Python example.
Output:
{'person': {'name': 'Kenn', 'sex': 'male', 'age': 28}}

The conversion of JSON data to Python is
based on the following conversion table
JSON Python
object dict
array list
string str
number (int) int
number (real) float
true True
false False
null None
.Here translation table show example of JSON objects to Python objects which are helpful to perform
decoding in Python of JSON string

Python to JSON (Encoding)
• we saw how to convert JSON into a Python value (i.e. Dictionary).
• Now, how we can convert (encode) a Python value to JSON? Converting
Python data to JSON is called an Encoding operation. Encoding is done with
the help of JSON library method – dumps()
• Serializing JSON refers to the transformation of data into a series of
bytes (hence serial) to be stored or transmitted across a network.
• To handle the data flow in a file, the JSON library in Python uses dump()
or dumps() function to convert the Python objects into their respective
JSON object, so it makes it easy to write data to files.

So this output is considered the data representation of the object (Dictionary). The method dumps()
was the key to such an operation.
Say that we have the following Dictionary in Python:

The conversion of Python objects to JSON data is based on
the following conversion table.
Python JSON
dict object
List, tuple array
str string
int number (int)
float number (real)
False false
True true
None null

• The keys in a Python dictionary have to be converted to a
string for them to be used as JSON data.
• However, a simple string conversion is only feasible for
basic types like str, int, float, and bool. For other types of
keys, this can result in a TypeError.
• we can avoid that from happening by setting the value of
skipkeys argument to True. This will tell Python to skip all
keys which cannot be converted to a string.

Method 1: Writing JSON to a file in Python using json.dumps()
We can convert any Python object to a JSON string and write JSON to File
using json.dumps() function and file.write() function respectively.
Following is a step by step process to write JSON to file.
1.Prepare JSON string by converting a Python Object to JSON string using
json.dumps() function.
2.Create a JSON file using open(filename, ‘w’) function. We are opening file
in write mode.
3. simply write JSON string to a file using the “write” function.
4. Close the JSON file.

Example 1: Write JSON (Object) to File
In this example, we will convert or dump a Python Dictionary to JSON String, and write this JSON string to a file
named data.json.
Python Program
Output
Run the above program, and data.json will be created in the working directory.

Example 3: Write JSON (List of Object) to File
In this example, we will convert or dump Python List of Dictionaries to JSON string, and write this JSON string to file
named data.json.
Python Program
Output
Run the above program, and data.json will be created in the working directory.
data.json

Method 2: Writing JSON to a file in Python using json.dump()
• Another way of writing JSON to a file is by using json.dump() method .
• The JSON package has the “dump” function which directly writes the
dictionary to a file in the form of JSON, without needing to convert it into an
actual JSON object.
It takes 2 parameters:
•dictionary – the name of a dictionary which should be converted to a JSON
object.
•file pointer – pointer of the file opened in write or append mode.

Format JSON code (Pretty print)
• The aim is to write well-formatted code for human understanding. With the help of
anyone can easily understand the code.
• To analyze and debug JSON data, we may need to print it in a more readable format.
This can be done by passing additional parameters indent and sort_keys to
json.dumps() and json.dump() method.
• sort_keys attribute in Python dumps function’s argument will sort the key in JSON in
ascending order. The sort_keys argument is a Boolean attribute. When it’s true
sorting is allowed otherwise not. Let’s understand with Python string to JSON sorting
example.

In the above program, have used 4 spaces for indentation. And, the keys are sorted in ascending order.
By the way, the default value of indent is None. And, the default value of sort_keys is False.

To better understand this, change indent to 40 and observe the output-

Output:
observe the keys age, cars, children, etc are arranged in
ascending order.

Back and Forth Conversion of Data
• The keys for dictionaries in Python can be of different data types like strings, int, or tuples. However,
the keys in JSON data can only be strings.
• This means that when you convert a dictionary into JSON, all its keys will be cast to strings.
Conversion of this JSON back to a dictionary will not get you back the original data type of the keys.

JSON_FIles-Py (2).pptx

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