Python json.JSONEncoder.encode() Method

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The Python json.JSONEncoder.encode() method is a method of the json.JSONEncoder class that directly encodes a Python object into a JSON-formatted string.

Unlike json.dumps(), which is a higher-level function, encode() provides lower-level control over the serialization process. It is typically used when customizing the behavior of JSON encoding in a subclass of JSONEncoder.

Syntax

Following is the syntax of the Python json.JSONEncoder.encode() method −

json.JSONEncoder().encode(obj)

Parameters

This method accepts the Python object as a parameter that needs to be serialized into a JSON-formatted string.

Return Value

This method returns a JSON-formatted string representation of the given Python object.

Example: Basic Usage of encode()

The encode() method can be used to convert basic Python objects into JSON-formatted strings −

import json

# Create an instance of JSONEncoder
encoder = json.JSONEncoder()

# Sample dictionary
data = {"name": "Alice", "age": 25, "city": "London"}

# Convert dictionary to JSON string
json_string = encoder.encode(data)

print("JSON Output:", json_string)

Following is the output obtained −

JSON Output: {"name": "Alice", "age": 25, "city": "London"}

Example: Custom JSON Encoding

We can subclass json.JSONEncoder to customize the encoding process and override the encode() method −

import json

# Custom JSON Encoder
class CustomEncoder(json.JSONEncoder):
   def encode(self, obj):
      # Add a custom message before encoding
      json_str = super().encode(obj)
      return f"CustomEncoded: {json_str}"

# Create an object of CustomEncoder
encoder = CustomEncoder()

# Sample dictionary
data = {"name": "Bob", "age": 30, "city": "New York"}

# Serialize using custom encoder
json_string = encoder.encode(data)

print("Custom JSON Output:", json_string)

We get the output as shown below −

Custom JSON Output: CustomEncoded: {"name": "Bob", "age": 30, "city": "New York"}

Example: Encoding a Custom Object

By default, json.JSONEncoder.encode() does not support encoding custom Python objects. We can override the default() method to enable custom object encoding −

import json

# Custom class
class Person:
   def __init__(self, name, age):
      self.name = name
      self.age = age

# Custom JSON Encoder
class PersonEncoder(json.JSONEncoder):
   def default(self, obj):
      if isinstance(obj, Person):
         return {"name": obj.name, "age": obj.age}
      return super().default(obj)

# Create an object of Person class
person = Person("Charlie", 40)

# Create an encoder instance
encoder = PersonEncoder()

# Serialize object using encode()
json_string = encoder.encode(person)

print("JSON Output:", json_string)

The result produced is as shown below −

JSON Output: {"name": "Charlie", "age": 40}

Example: Pretty-Printing JSON

We can use the indent parameter in json.JSONEncoder to format the JSON output for better readability −

import json

# Create an instance of JSONEncoder with indentation
encoder = json.JSONEncoder(indent=4)

# Sample dictionary
data = {"name": "Alice", "age": 25, "city": "London"}

# Convert dictionary to formatted JSON string
json_string = encoder.encode(data)

print("Pretty-Printed JSON Output:")
print(json_string)

After executing the above code, we get the following output −

Pretty-Printed JSON Output:
{
    "name": "Alice",
    "age": 25,
    "city": "London"
}

Example: Using separators Parameter

The separators parameter allows customization of JSON formatting −

import json

# Create an instance of JSONEncoder with custom separators
encoder = json.JSONEncoder(separators=(",", ":"))

# Sample dictionary
data = {"name": "Alice", "age": 25, "city": "London"}

# Convert dictionary to JSON with custom separators
json_string = encoder.encode(data)

print("Compact JSON Output:", json_string)

Following is the output obtained −

Compact JSON Output: {"name":"Alice","age":25,"city":"London"}