Amazon Textract
Developer Guide

Extracting Key-Value Pairs from a Form Document

The following Python example shows how to extract key-value pairs in form documents from Block objects that are stored in a map. Block objects are returned from a call to AnalyzeDocument. For more information, see Form Data (Key-Value Pairs).

The functions that are specific to Amazon Textract are:

  • get_kv_map – Calls AnalyzeDocument, and stores the KEY and VALUE BLOCK objects in a map.

  • get_kv_relationship and find_value_block – Constructs the key-value relationships from the map.

Note

You can download the source file from textract_python_kv_parser.py.

To extract key-value pairs from a form document

  1. Configure your environment. For more information, see Prerequisites.

  2. Save the following example code to a file named textract_python_kv_parser.py.

    import boto3 import sys import re import json def get_kv_map(file_name): with open(file_name, 'rb') as file: img_test = file.read() bytes_test = bytearray(img_test) print('Image loaded', file_name) # process using image bytes client = boto3.client('textract') response = client.analyze_document(Document={'Bytes': bytes_test}, FeatureTypes=['FORMS']) # Get the text blocks blocks=response['Blocks'] # get key and value maps key_map = {} value_map = {} block_map = {} for block in blocks: block_id = block['Id'] block_map[block_id] = block if block['BlockType'] == "KEY_VALUE_SET": if 'KEY' in block['EntityTypes']: key_map[block_id] = block else: value_map[block_id] = block return key_map, value_map, block_map def get_kv_relationship(key_map, value_map, block_map): kvs = {} for block_id, key_block in key_map.items(): value_block = find_value_block(key_block, value_map) key = get_text(key_block, block_map) val = get_text(value_block, block_map) kvs[key] = val return kvs def find_value_block(key_block, value_map): for relationship in key_block['Relationships']: if relationship['Type'] == 'VALUE': for value_id in relationship['Ids']: value_block = value_map[value_id] return value_block def get_text(result, blocks_map): text = '' if 'Relationships' in result: for relationship in result['Relationships']: if relationship['Type'] == 'CHILD': for child_id in relationship['Ids']: word = blocks_map[child_id] if word['BlockType'] == 'WORD': text += word['Text'] + ' ' if word['BlockType'] == 'SELECTION_ELEMENT': if word['SelectionStatus'] == 'SELECTED': text += 'X ' return text def print_kvs(kvs): for key, value in kvs.items(): print(key, ":", value) def search_value(kvs, search_key): for key, value in kvs.items(): if re.search(search_key, key, re.IGNORECASE): return value def main(file_name): key_map, value_map, block_map = get_kv_map(file_name) # Get Key Value relationship kvs = get_kv_relationship(key_map, value_map, block_map) print("\n\n== FOUND KEY : VALUE pairs ===\n") print_kvs(kvs) # Start searching a key value while input('\n Do you want to search a value for a key? (enter "n" for exit) ') != 'n': search_key = input('\n Enter a search key:') print('The value is:', search_value(kvs, search_key)) if __name__ == "__main__": file_name = sys.argv[1] main(file_name)
  3. At the command prompt, enter the following command. Replace file with the document image file that you want to analyze.

    textract_python_kv_parser.py file
  4. When you're prompted, enter a key that's part of the input document. If the key is detected, the program displays the value that's associated with the key.