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# 從表單文件中擷取鍵值對
<a name="examples-extract-kvp"></a>

下列 Python 範例示範如何從儲存在映射中的[封鎖](https://docs.aws.amazon.com/textract/latest/APIReference/API_Block.html)物件擷取形式文件中的鍵/值對。區塊物件會從對 [AnalyzeDocument](https://docs.aws.amazon.com/textract/latest/APIReference/API_AnalyzeDocument.html) 的呼叫傳回。如需詳細資訊，請參閱[表單資料 （鍵值對）](how-it-works-kvp.md)。

您可以使用下列函數：
+ `get_kv_map` – 呼叫 [AnalyzeDocument](https://docs.aws.amazon.com/textract/latest/APIReference/API_AnalyzeDocument.html)，並將 KEY 和 VALUE BLOCK 物件存放在地圖中。
+ `get_kv_relationship` 和 `find_value_block` – 從地圖建構鍵值關係。

**從表單文件中擷取鍵/值對**

1. 設定您的環境。如需詳細資訊，請參閱[先決條件](examples-blocks.md#examples-prerequisites)。

1. 將下列範例程式碼儲存至名為 *textract\_python\_kv\_parser.py *的檔案。在函數 中`get_kv_map`，`profile-name`將 取代為可擔任角色的設定檔名稱，並將 `region`取代為您要執行程式碼的區域。

   ```
   import boto3
   import sys
   import re
   import json
   from collections import defaultdict
   
   
   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
       session = boto3.Session(profile_name='profile-name')
       client = session.client('textract', region_name='region')
       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 = defaultdict(list)
       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].append(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)
   ```

1. 在命令提示字元中，輸入下列命令。`file` 將 取代為您要分析的文件映像檔案。

   ```
   python textract_python_kv_parser.py {{file}}
   ```

1. 出現提示時，請輸入輸入文件中的金鑰。如果程式碼偵測到金鑰，則會顯示金鑰的值。