use for loop to add elements to an existing dictionary in a list

Question

I have the following list of dictionaries:

d = [{'Sport': 'MLB', 'Position': 'SP', 'Age': '25'},
     {'Sport': 'NBA', 'Position': 'PG', 'Age': '28'}]

I have another list that i would like to append to the above by using a for loop:

c = [{'2015 Salary' : '25'}, {'2015 Salary': '35'},
    {'2016 Salary' : '30'}, {'2016 Salary' : '40'}]

I would like the final output to be

e = [{'Sport': 'MLB', 'Position': 'SP', 'Age': '25', '2015 Salary': '25',  
     '2016 Salary': '30'},
     {'Sport': 'NBA', 'Position': 'PG', 'Age': '28', '2015 Salary': '35',  
     '2016 Salary': '40'}}]

The positions would always be the same thats why i was going to use a for loop.

Adam Smith · Accepted Answer · 2018-07-24T14:57:59.730

7

You could use itertools.cycle to repeat over d while updating from c.

import itertools

for existing, new_dict in zip(cycle(d), c):
    existing.update(new_dict)

cycle turns a list into an infinite list by restarting from the beginning whenever it is exhausted. When you zip them together, cycle(d) and c pair up to give:

({'Sport': 'MLB', 'Position': 'SP', 'Age': '25'}, {' 2015 Salary' : '25'})
({'Sport': 'NBA', 'Position': 'PG', 'Age': '28'}, {'2015 Salary': '35'})
({'Sport': 'MLB', 'Position': 'SP', 'Age': '25'}, {'2016 Salary ': '30'})
({'Sport': 'NBA', 'Position': 'PG', 'Age': '28'}, {'2016 Salary' : '40'})

Which then update d to your expected output.

edited Jul 24 '18 at 14:57

answered Jul 24 '18 at 14:49

Adam Smith

52,157
12
73
112

i wouldnt want to create 2 new dictionaries tho, i would only want 2 total. – skimchi1993 Jul 24 '18 at 14:52
@skimchi1993 I'm not sure what that means. No new dictionaries are being created here. `d` is being updated in-place. – Adam Smith Jul 24 '18 at 14:53
1

@skimchi1993 Those four lines in the end are just the pairings, not the resulting list of dicts. – tobias_k Jul 24 '18 at 14:55
@tobias_k OH! I can see how that's confusing, let me edit it to be a bit clearer (good catch) – Adam Smith Jul 24 '18 at 14:57
1

@AdamSmith, I didn't know about the `cycle` function. This is a very impressive answer. – lmiguelvargasf Jul 24 '18 at 15:17

lmiguelvargasf · Answer 2 · 2018-07-24T14:54:50.597

1

You can achieve it by:

for i, current_d in enumerate(d):
    current_l = c[i::2]
    for e in current_l:
        current_d.update(e)

d will contain the information that you want.

edited Jul 24 '18 at 14:54

answered Jul 24 '18 at 14:40

lmiguelvargasf

63,191
45
217
228

This does not work because c is a longer list than d, and it only adds the 2015 salaries – MoxieBall Jul 24 '18 at 14:44
@MxieBall, I agree with you. I hope the one who asked the question updates it. – lmiguelvargasf Jul 24 '18 at 14:45
in my case, they wont be hte same length, is this not possible then? – skimchi1993 Jul 24 '18 at 14:47
After the edit this still only adds the 2015 salaries – MoxieBall Jul 24 '18 at 14:51
@skimchi1993, I have updated my answer. – lmiguelvargasf Jul 24 '18 at 15:02

score 1 · Answer 3 · answered Jul 24 '18 at 14:55

1

Hope this may help

for i in range(len(d)):
     for j in range(i,len(c),i+2):
             d[i].update(c[j])

answered Jul 24 '18 at 14:55

Ravinder Baid

395
1
15

Laurent H. · Answer 4 · 2018-07-24T15:05:36.850

Here is my one-line style solution using comprehensions, without any needed import, and which works also whatever the length of d input:

d = [{'Sport': 'MLB', 'Position': 'SP', 'Age': '25'},
     {'Sport': 'NBA', 'Position': 'PG', 'Age': '28'}]

c = [{'2015 Salary': '25'}, {'2015 Salary': '35'},
     {'2016 Salary': '30'}, {'2016 Salary': '40'}]

result = [{k:v for i in ([d[j]] + c[j::len(d)]) for k,v in i.items()} for j in range(len(d))]

print(result)
# [{'Sport': 'MLB', 'Position': 'SP', 'Age': '25', '2015 Salary': '25', '2016 Salary': '30'},
#  {'Sport': 'NBA', 'Position': 'PG', 'Age': '28', '2015 Salary': '35', '2016 Salary': '40'}]

use for loop to add elements to an existing dictionary in a list

4 Answers4