CODEWITHSUNDEEP
pythondictionary
Joe F.
Joe F.

Reputation: 867

Return value from Python dict based on evaluation of other key/value pairs

I have three Python dictionaries like so:

dict_1 = {
    'Id':'001',
    'CreatedDate':'2017-04-24T06:49:28.000Z',
    'FirstName':'R',
    'LastName':'Hendrix',
    'Company':'Hooli',
    'Age':29
    }

dict_2 = {
    'Id':'002',
    'CreatedDate':'2010-01-23T06:49:28.000Z',
    'FirstName':'Richard',
    'LastName':'Hendricks',
    'Company':'Pied Piper',
    'Age':30
    }

dict_3 = {
    'Id':'003',
    'CreatedDate':'2013-01-23T06:49:28.000Z',
    'FirstName':'Richard',
    'LastName':'Hendricks',
    'Company':'Pied Piper',
    'Age':31
    }

I want to create functions to get the newest or oldest values from these dictionaries based on the CreatedDate value.

I imagine I would need to put all of these dicts in a list:

list_of_dicts = [dict_1, dict_2, dict_3]

An function might work like so:

def get_newest(
    list_of_dicts, 
    created_date_fieldname='CreatedDate',
    return_field='Company'
    ):
    # TODO - take in two or more dicts, and return the newest Company
    # value based on CreatedDate field.

Upvotes: 0

Views: 147

Answers (2)

Nilanjan
Nilanjan

Reputation: 176

You can use max and min built-in function.

>>> from datetime import datetime
>>> def get_newest(list_of_dicts, created_date_fieldname='CreatedDate', return_field='Company'):
...     return max(list_of_dicts, key=lambda x: datetime.strptime(x[created_date_fieldname], "%Y-%m-%dT%H:%M:%S.%fZ"))[return_field]
... 
>>> print get_newest(list_of_dicts)
Hooli

Upvotes: 0

vallentin
vallentin

Reputation: 26207

You could use datetime.strptime() to parse the dates, then after that you just compare them until you've found the newest date.

from datetime import datetime

def get_newest(list_of_dicts, created_date_fieldname='CreatedDate', return_field='Company'):
    if not list_of_dicts:
        return None
    newest = list_of_dicts[0]
    for current in list_of_dicts:
        newest_date = datetime.strptime(newest[created_date_fieldname], "%Y-%m-%dT%H:%M:%S.%fZ")
        current_date = datetime.strptime(current[created_date_fieldname], "%Y-%m-%dT%H:%M:%S.%fZ")
        if current_date >= newest_date:
            newest = current
    return newest[return_field]

Now doing print(get_newest(list_of_dicts)) (given your data) would output:

Hooli

Note that if there's multiple instances of the newest date. Then the last instance will be selected. If you instead what the first instance, then use current_date > newest_date instead.

Upvotes: 1

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