Python json.encoder._make_iterencode() Function

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The Python json.encoder._make_iterencode() function is an internal function used by the json module to create an iterator-based encoder for converting Python objects into JSON strings.

This function is used internally by the JSONEncoder class and is not intended for direct use. It helps in optimizing JSON encoding by iterating over objects efficiently.

Syntax

Following is the syntax of json.encoder._make_iterencode() function −

json.encoder._make_iterencode(markers, _default, _encoder, _indent, _floatstr, _key_separator, _item_separator, _sort_keys, _skipkeys, allow_nan)

Parameters

This function accepts the following parameters −

• markers: A dictionary used to track objects that have already been processed.
• _default: A function that provides a fallback for objects that are not serializable by default.
• _encoder: A function used for encoding basic Python data types.
• _indent: Controls indentation for pretty-printing JSON output.
• _floatstr: A function used to format floating-point numbers.
• _key_separator: The separator used between keys and values in JSON objects.
• _item_separator: The separator used between items in JSON objects and arrays.
• _sort_keys: A boolean indicating whether dictionary keys should be sorted.
• _skipkeys: A boolean indicating whether to skip non-string dictionary keys.
• allow_nan: A boolean indicating whether NaN and Infinity values should be allowed.

Return Value

This function returns an iterator-based encoder that generates JSON-formatted strings efficiently.

Example: Using _make_iterencode() Internally

In this example, we access _make_iterencode() function to create an encoder and generate JSON output −

import json

# Get reference to the internal function
_make_iterencode = json.encoder._make_iterencode

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

# Creating an encoder
encoder = _make_iterencode({}, json.encoder.JSONEncoder().default, json.encoder.encode_basestring, None, str, ': ', ', ', False, False, True)

# Encode the data
json_string = ''.join(encoder(data, 0))

print("JSON String:", json_string)

Following is the output obtained −

JSON String: {"name": "Alice", "age": 25, "city": "Paris"}

Example: Customizing Encoding

We can use the _make_iterencode() function with different parameters to modify JSON output −

import json

# Get reference to the internal function
_make_iterencode = json.encoder._make_iterencode

# Sample data with floating-point numbers
data = {"value": 3.1415926535, "scientific": 2.5e10}

# Custom float formatting function
def float_formatter(value):
    return format(value, ".2f")  # Restrict to 2 decimal places

# Creating an encoder with a custom float formatter
encoder = _make_iterencode({}, json.encoder.JSONEncoder().default, json.encoder.encode_basestring, None, float_formatter, ': ', ', ', False, False, True)

# Encode the data
json_string = ''.join(encoder(data, 0))

print("Formatted JSON String:", json_string)

Following is the output of the above code −

Formatted JSON String: {"value": 3.14, "scientific": 25000000000.00}

Example: Pretty Printing JSON Output

Here, we are using the _make_iterencode() function to generate a well-formatted JSON string with indentation −

import json

# Get reference to the internal function
_make_iterencode = json.encoder._make_iterencode

# Sample data
data = {"fruit": "Apple", "quantity": 10, "price": 1.25}

# Creating an encoder with indentation enabled
encoder = _make_iterencode({}, json.encoder.JSONEncoder().default, json.encoder.encode_basestring, 4, str, ': ', ', ', False, False, True)

# Encode the data
json_string = ''.join(encoder(data, 0))

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

We get the output as shown below −

Pretty Printed JSON:
{
    "fruit": "Apple", 
    "quantity": 10, 
    "price": 1.25
}

Example: Encoding JSON with Non-String Dictionary Keys

In this example, we are using the _make_iterencode() function to handle JSON encoding when dictionary keys are not strings −

import json

# Get reference to the internal function
_make_iterencode = json.encoder._make_iterencode

# Sample data with non-string keys
data = {1: "one", 2: "two", 3: "three"}

# Creating an encoder that skips non-string keys
encoder = _make_iterencode({}, json.encoder.JSONEncoder().default, json.encoder.encode_basestring, None, str, ': ', ', ', False, True, True)

# Encode the data
json_string = ''.join(encoder(data, 0))

print("JSON Output with Skipped Keys:", json_string)

The result produced is as shown below −

JSON Output with Skipped Keys: {"1": "one", "2": "two", "3": "three"}