Group dictionary in a list of dictionaries by the first letter of a Value

January 4, 2022

I’m having a list of dictionaries that looks like this:

  [{
    'Host-id': 'W000644',
    'Email': 'Hotmail',
    'Color': 'red',
    'Timestamp': '12-10-2021'
    },
    {
    'Host-id': 'W000955',
    'Email': 'Hotmail',
    'Color': 'red',
    'Timestamp': '12-10-2021'
    },
    {
    'Host-id': 'K000003',
    'Email': 'Gmail',
    'Color': 'green',
    'Timestamp': '15-11-2021'
    },
    'Host-id': 'G000004',
    'Email': 'Colemail',
    'Color': 'blue',
    'Timestamp': '14-11-2021'
    },
    {
    'Host-id': 'S000002',
    'Email': 'Gmail',
    'Color': 'blue',
    'Timestamp': '22-10-2021'
    },
    {
    'Host-id': 'G000003',
    'Email': 'spam',
    'Color': 'red',
    'Timestamp': '12-11-2021'
    }]

I want to group it, using the first letter of the ‘Host-Id’ Value (like ‘W’ for Water or ‘G’ for Gas) so it looks finally like this:

  {
    "Water": [
          {
         'Host-id': 'W000644',
         'Email': 'Hotmail',
         'Color': 'red',
         'Timestamp': '12-10-2021'
         },
         {
         'Host-id': 'W000955',
         'Email': 'Hotmail',
         'Color': 'red',
         'Timestamp': '12-10-2021'
         }
   ],

   "Gas":[
        {
        'Host-id': 'G000004',
        'Email': 'Colemail',
        'Color': 'blue',
        'Timestamp': '14-11-2021'
        }, 
        {
        'Host-id': 'G000003',
        'Email': 'spam',
        'Color': 'red',
        'Timestamp': '12-11-2021'
       } 
     ]
   }

Unfortunately I have no idea where to start. I have tried it with a loop but it looks overly complex and didnt yield the results I wanted. Could anyone please point me into the right direction?

Thank you in advance

>Solution :

I can recommend PyFunctional library for your task. It could be done without loops like this

from functional import seq

lst = [
    {
        'Host-id': 'W000644',
        'Email': 'Hotmail',
        'Color': 'red',
        'Timestamp': '12-10-2021'
    },
    {
        'Host-id': 'W000955',
        'Email': 'Hotmail',
        'Color': 'red',
        'Timestamp': '12-10-2021'
    },
    {
        'Host-id': 'G000004',
        'Email': 'Colemail',
        'Color': 'blue',
        'Timestamp': '14-11-2021'
    },
    {
        'Host-id': 'G000003',
        'Email': 'spam',
        'Color': 'red',
        'Timestamp': '12-11-2021'
    }
]

KEY_MAP = {
    "W": "Water",
    "G": "Gas",
}

s = seq(lst)
res = s.group_by(lambda x: KEY_MAP[x['Host-id'][0]])
print(res.to_dict())

Output

{
    'Water': [
        {'Host-id': 'W000644', 'Email': 'Hotmail', 'Color': 'red', 'Timestamp': '12-10-2021'},
        {'Host-id': 'W000955', 'Email': 'Hotmail', 'Color': 'red', 'Timestamp': '12-10-2021'}
    ],
    'Gas': [
        {'Host-id': 'G000004', 'Email': 'Colemail', 'Color': 'blue', 'Timestamp': '14-11-2021'},
        {'Host-id': 'G000003', 'Email': 'spam', 'Color': 'red', 'Timestamp': '12-11-2021'}
    ]
}