for loops reduction to list comprehension or use of lambda function-CodePudding

categories = [
  {
    "CategoryUId": "f34cc7a8-ac38-4f1f-a637-08bd034d74f3",
    "SubCategory": [
      {
        "SubCategoryUId": "9b37dbf3-4b4d-4bbb-8bc4-2ce036b69042"
      },
      {
        "SubCategoryUId": "d4131c98-9823-4354-b587-c736cd77df4d"
      }
    ]
  },
  {
    "CategoryUId": "460366f6-c8ef-4e4e-80a7-4ace9c59122c",
    "SubCategory": [
      {
        "SubCategoryUId": "ed6dbfb9-bc1a-4161-b040-f9aba55c995a"
      },
      {
        "SubCategoryUId": "06246a88-fe8a-42fa-aba6-3393af463397"
      },
      {
        "SubCategoryUId": "2f37fd26-fae5-4dc4-9f10-4e87a2f5ae68"
      }
    ]
  }
]

A basic example where is categories is a list of dictionaries.

for item in categories:
    categoryUId = item['CategoryUId']
    for value in item['SubCategory']:
        subcategory = value['SubCategoryUId']
        subcategoryList.append(subcategory)
    dict = {categoryUId : subcategoryList}

I am going through some random python exercises, is it possible to use lambda function or the List comprehension for the above mentioned code snippet.

Please assist me with an approach.

CodePudding user response：

It seems this is the outcome you expected:

out = {d['CategoryUId']: [v['SubCategoryUId'] for v in d['SubCategory']] for d in categories}

The above code with a lambda in map (extremely ugly though; do not recommend):

out = dict(map(lambda d: (d['CategoryUId'], [*map(lambda v:v['SubCategoryUId'], d['SubCategory'])]), categories))

Output:

{'f34cc7a8-ac38-4f1f-a637-08bd034d74f3': ['9b37dbf3-4b4d-4bbb-8bc4-2ce036b69042',
  'd4131c98-9823-4354-b587-c736cd77df4d'],
 '460366f6-c8ef-4e4e-80a7-4ace9c59122c': ['ed6dbfb9-bc1a-4161-b040-f9aba55c995a',
  '06246a88-fe8a-42fa-aba6-3393af463397',
  '2f37fd26-fae5-4dc4-9f10-4e87a2f5ae68']}