How to get individual fields in list of dictionary

Question

I have a list of dictionaries called dictList that has data like so:
[{'id': '5', 'total': '39'}, {'id': '5', 'total': '43'}].

I am trying to create a new dictionary that uses the id as the key and total as the value.

So have tried this:

keys = [d['id'] for d in dictList]
values = [d['total'] for d in dictList]

new_dict[str(keys)]= values

However the output is: {"['5', '5']": [39, 43]}

I am not sure what is going on, I am just trying to get the id and the respective total like 5, 39 and 5, 43 in to new_dict.

EDIT:
Please note that dictList contains all the products with ID 5. There are other fields, but I didn’t include them.

Asked By: efiemu

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Source

Answer 1

One approach:

data = [{'id': '5', 'total': '39'}, {'id': '5', 'total': '43'}]

res = {}
for d in data:
    key = d["id"]
    if key not in res:
        res[key] = 0
    res[key] += int(d["total"])

print(res)

Output

{'5': 82}

Alternative using collections.defaultdict:

from collections import defaultdict

data = [{'id': '5', 'total': '39'}, {'id': '5', 'total': '43'}]

res = defaultdict(int)
for d in data:
    key = d["id"]
    res[key] += int(d["total"])

print(res)

Output

defaultdict(<class 'int'>, {'5': 82})

Answered By: Dani Mesejo

Answer 2

Use sorted and itertools.groupby to group by the 'id' key of each list element:

import itertools

dictList = [{'id': '5', 'total': '39'}, {'id': '10', 'total': '10'},
            {'id': '5', 'total': '43'}, {'id': '10', 'total': '22'}]

groups = itertools.groupby(sorted(dictList, key=lambda item: item['id'])
                           , key=lambda item: item['id'])

Next, take the sum of each group:

product_totals = {
    key: sum(int(item['total']) for item in grp)
    for key, grp in groups
}

Which gives:

{'10': 32, '5': 82}

If you have lots of such entries, you could consider using pandas to create a dataframe. Pandas has vectorized methods that help you crunch numbers faster. The idea behind finding the sum of totals is the same, except in this case we don’t need to sort because pandas.groupby takes care of that for us

>>> import pandas as pd

>>> df = pd.DataFrame(dictList)
>>> df['total'] = df['total'].astype(int)
>>> df
   id total
0   5    39
1  10    10
2   5    43
3  10    22

>>> df.groupby('id').total.sum()
id
10    32
5     82
Name: total, dtype: int32

>>> df.groupby('id').total.sum().as_dict()
 {'10': 32, '5': 82}

Answered By: Pranav Hosangadi

Answer 3

Although I’m not sure what you are trying to do, try this:

for d in dictlist:
    if new_dict[d["id"]]:
        new_dict[d["id"]] += d["total"]
    else:
        new_dict[d["id"]] = d["total"]

Answered By: Cavalex

How to get individual fields in list of dictionary

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