Question

I want to join the dictionaries in a list whose key ‘user’ are the same, but I don’t realize how. for example:

[{'count2': 34, 'user': 2},
 {'count4': 233, 'user': 2},
 {'count2': 234, 'user': 4},
 {'count4': 344, 'user': 5}]

would become:

[{'count2': 34, 'count4': 233, 'user': 2 },
 {'count2': 234, 'user': 4},
 {'count4': 344, 'user': 5}]

I searched extensively without found something similar in stack overflow, any help would be greatly appreciated.

Answer 1

Something like this should work. But there are probably more efficient ways to do it (and in fewer lines)…

# Input
a=[{'count2': 34, 'user': 2},
 {'count4': 233, 'user': 2},
 {'count2': 234, 'user': 4},
 {'count4': 344, 'user': 5}]

# Get set of unique users
u=list(set([x['user'] for x in a]))

# Create a blank list of dictionaries for the result
r=[{}] * len(u)

# Iterate over input and add the dictionaries together
for x in a:
    r[u.index(x['user'])] = dict(r[u.index(x['user'])].items() + x.items())


>>> r
[{'count2': 34, 'user': 2, 'count4': 233}, {'count2': 234, 'user': 4}, {'count4': 344, 'user': 5}]