Merging two list of dictionary in python

Question

lst1 = [
    {'mem': '20.0', 'name': 'p1', 'cpu': '20.0'}, 
    {'mem': '20.0', 'name': 'p2', 'cpu': '20.0'},
    {'mem': '20.0', 'name': 'p3', 'cpu': '20.0'}, 
    {'mem': '20.0', 'name': 'p4', 'cpu': '20.0'}
]

lst2 = [
    {'pid': 814, 'name': 'p1'},
    {'pid': 999, 'name': 'p2'},
    {'pid': 1006, 'name': 'p3'},
    {'pid': 1152, 'name': 'p4'}
]

I need to merge above two list into single list i.e.

lst3 = [
    {'mem': '20.0', 'name': 'p1', 'cpu': '20.0', 'pid':814}, 
    {'mem': '20.0', 'name': 'p2', 'cpu': '20.0','pid':999},
    {'pid': 1006, 'mem': '20.0', 'name': 'p3', 'cpu': '20.0'},
    {'pid': 1152,'mem': '20.0', 'name': 'p4', 'cpu': '20.0'}
]

I have tried doing it in below way

lst3 = list()
test = dict()
for f,b in zip(lst1,lst2):
    test = f.copy()
    test.update(b)
    #print test
    lst3.append(test)

print lst3

Please let me know is there any easy method or more pythonic way to do this

Possible duplicate of [How to concatenate two lists in Python?](https://stackoverflow.com/questions/1720421/how-to-concatenate-two-lists-in-python) — peachykeen, Jun 27 '18 at 18:29
Possible duplicate of [join two lists of dictionaries on a single key](https://stackoverflow.com/questions/5501810/join-two-lists-of-dictionaries-on-a-single-key) — tourist, Jun 27 '18 at 18:38

user3483203 · Answer 1 · 2018-06-27T18:41:42.067

Just use zip and merge, as long as both lists are ordered relative to each other:

out = [{**i, **j} for i, j in zip(lst1, lst2)]

# Result

[{'cpu': '20.0', 'mem': '20.0', 'name': 'p1', 'pid': 814},
 {'cpu': '20.0', 'mem': '20.0', 'name': 'p2', 'pid': 999},
 {'cpu': '20.0', 'mem': '20.0', 'name': 'p3', 'pid': 1006},
 {'cpu': '20.0', 'mem': '20.0', 'name': 'p4', 'pid': 1152}]

Matches output:

In [292]: out == lst3
Out[292]: True

If the lists are not guaranteed to be sorted, you can sort on the common key, in this case name, before applying my method:

lst1, lst2 = (sorted(i, key=lambda x: x['name']) for i in [lst1, lst2])

Personally, I think your current method works fine, and it is very clear what you are doing. Also, my method of merging exclusively works in Python 3.5+

score 0 · Answer 2 · answered Dec 17 '22 at 09:09

l1 = [{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test1'}]
l2 = [{'id': 3, 'age': 10},{'id': 4, 'age': 10},{'id': 1, 'age': 10}, {'id': 2, 'age': 20}]


def m1(l1,l2):
    d = defaultdict(dict)
    for l in (l1,l2):
        for d1 in l :
            d[d1['id']].update(d1)
    aa = sorted(d.values(),key = itemgetter('id'))
    aap = print(aa)
    return aap        
            
m1(l1,l2)            
                        
"""
output :
[{'id': 1, 'name': 'test', 'age': 10}, {'id': 2, 'name': 'test1', 'age': 20}, {'id': 3, 'age': 10}, {'id': 4, 'age': 10}]
"""

Merging two list of dictionary in python

2 Answers2