Python json.decoder.JSONArray() Function

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The Python json.decoder.JSONArray() function is an internal helper function used to parse JSON arrays.

This function is primarily used by the JSON decoder when parsing array structures from a JSON-encoded string.

Syntax

Following is the syntax of the Python json.decoder.JSONArray() function −

json.decoder.JSONArray(s_and_end, scan_once, **kwargs)

Parameters

This function accepts the following parameters −

  • s_and_end: A tuple containing the JSON string and the index position to start parsing.
  • scan_once: A function used for scanning JSON values.
  • **kwargs: Additional keyword arguments.

Return Value

This function returns a tuple containing the parsed list and the index position where parsing stopped.

Example: Basic Usage

In this example, we use the json.decoder.JSONArray() function to parse a JSON array −

import json.decoder

# JSON-encoded array
json_string = '[1, 2, 3]'

# Define scan_once function properly
scan_once = json.decoder.JSONDecoder().scan_once

# Parse JSON array using JSONArray()
parsed_array, end_index = json.decoder.JSONArray((json_string, 1), scan_once)

print("Parsed Array:", parsed_array)
print("End Index:", end_index)

Following is the output of the above code −

Parsed Array: [1, 2, 3]
End Index: 9

Example: Parsing Nested JSON Arrays

The JSONArray() function can also handle nested JSON arrays −

import json.decoder

# JSON-encoded nested array
json_string = '[[1, 2], [3, 4]]'

# Get the scan_once function from JSONDecoder
scan_once = json.decoder.JSONDecoder().scan_once

# Parse JSON array using JSONArray()
parsed_array, end_index = json.decoder.JSONArray((json_string, 1), scan_once)

print("Parsed Nested Array:", parsed_array)
print("End Index:", end_index)

Following is the output obtained −

Parsed Nested Array: [[1, 2], [3, 4]]
End Index: 16

Example: Handling Empty JSON Arrays

The function correctly handles empty JSON arrays −

import json.decoder

# JSON-encoded empty array
json_string = '[]'

# Define scan_once function
def scan_once(s, idx):
   return json.decoder.scanstring(s, idx)

# Parse JSON array
parsed_array, end_index = json.decoder.JSONArray((json_string, 1), scan_once)

print("Parsed Empty Array:", parsed_array)
print("End Index:", end_index)

We get the output as shown below −

Parsed Empty Array: []
End Index: 2

Example: Handling Invalid JSON Arrays

If the input is not a valid JSON array, a ValueError is raised −

import json.decoder

# Invalid JSON-encoded array (missing closing bracket)
json_string = '[1, 2, 3'

# Get the scan_once function from JSONDecoder
scan_once = json.decoder.JSONDecoder().scan_once

try:
   # Attempt to parse an invalid JSON array
   parsed_array, end_index = json.decoder.JSONArray((json_string, 1), scan_once)
   print("Parsed Array:", parsed_array)
except ValueError as e:
   print("Error:", e)

The result produced is as follows −

Error: Expecting ',' delimiter: line 1 column 9 (char 8)
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